Tunachicken is the tinned chicken in the tuna sized can. Sproil is the spray oil. Having the greyling at a cafeteria is going for the dull, but probably safest choice. Refrigerator tapas is whatever small meals we can scrounge to make one whole meal when we really need to shop.

Our family has a lot of private coinages like that also, and retelling the etymology of them is part of their enjoyment. But I've never thought of those terms as constituting slang. To me, slang is language that's socially unacceptable, usually on the racy side. (I expect condemnations of elitism.) Rather than "private slang", to me family coinages are private jargon, not slang.

On a separate note, any theories on the origin of the word "slang"?

In my family there were a number of words (usually shortened forms) which we children knew (or more specifically had had time to discover) were not used by other people, and our family used them for fun. But my youngest sister, born many years after us older ones, grew up thinking that these were normal everyday words, so she sometimes had trouble at school and with her own friends by using those words and insisting they were normal. No one else had thought that this family jargon needed explaining.

I knew a Taiwan Chinese family from the mainland whose parents spoke two different dialects, neither of them Mandarin or Hokkien. They developed a private language of their own usable only within the family.

To me, slang is language that's socially unacceptable, usually on the racy side. (I expect condemnations of elitism.) Rather than "private slang", to me family coinages are private jargon, not slang.

In the Wiki definition of slang it says that two licensed linguists,

Bethany K. Dumas and Jonathan Lighter argue that an expression should be considered "true slang" if it meets at least two of the following criteria:
It lowers, if temporarily, "the dignity of formal or serious speech or writing"; in other words, it is likely to be seen in such contexts as a "glaring misuse of register."
Its use implies that the user is familiar with whatever is referred to, or with a group of people that are familiar with it and use the term.
"It is a taboo term in ordinary discourse with people of a higher social status or greater responsibility."
It replaces "a well known conventional synonym." This is done primarily to avoid "the discomfort caused by the conventional item [or by] further elaboration."
Slang should be distinguished from jargon, which is the technical vocabulary of a particular profession. Jargon, like many examples of slang, may on occasion be used to exclude non-group members from the conversation, but in general has the function of allowing its users to talk precisely about technical issues in a given field.

I'd propose a different definition.

Slang is a word or phrase which is comprehensible to, and used by, a definable social group of indeterminate size, but which is not immediately comprehensible to, and rarely (if ever used) by those outside the social group. It will rarely if ever be used in formal settings, but may in time become widespread outside the original social group, so that the definable social group becomes everyone in a geographic area or even a country.

As illustration of this, there is the word "score", which when I was a young man (which was a considerable time ago), was used by my peer group (late adolescence to twentysomethings) to refer to sex, preferably of the causal one night stand variety. It has now been replaced, apparently, by the term "hook-up". Meanwhile, the original usage expanded both in meaning and in the groups among which it was used to signify attaining something valuable (generally) or accessible only with some difficulty--say, the degree of difficulty involved in coaxing a young woman into casual sex. Thus, "I scored some tickets to the Knicks-Net game". And notice that the expanded meaning, unlike the original meaning, does not satisfy the final Dumas-Lighter condition, since there is no real discomfort caused by the conventional synonym.

Not bad, but I thought 'score' first meant buying drugs -- that was the sequence I heard it, at any rate. Do you have evidence that sex came before drugs?

"Score" came from sports: "first base, second base" etc., but the word was only used by greasers and guys with poor grades who hadn't figured out that sex was a lot more complicated than just making conquests. These guys tended to end up marrying their pregnant girlfriends. Using "score" for obtaining street drugs I first heard around 1970. It was much later it came to be used for ordinary purchases--maybe as a way of sending code to someone else to see whether another code would be returned and the topic of drugs could be broached with confidentiality.

Kind of like 'panties', then. The movie 'Shaft's Big Score' was released in 1972.

The Amazon reviews don't say what Shaft's "score" was--since he was a defender of the law it wasn't drugs, and if "MGM upgraded the series, giving more action scenes and less nudity" it probably wasn't sex, so that leaves the "cool quarter of a million dollars" from the friend's office safe. Ergo, by 1972 "score" had either become generic or was still being used in the sports sense.

BTW, here is a really nifty pet video. It's got cats in it.

It was drugs, I saw it.

Slang is like obscenity, I can't necessarily define it very well but I know it when I hear it.

A couple of aspects of slang that need to be included in any definition.

It doesn't follow standard usage, but doesn't challenge standard usage either (though it may overtake and replace it under some circumstances).

It can't be addressed to everyone and properly should annoy those it's not addressed to.

If it was drugs, then there's a double entendre in the title: "shaft/score"--both have sexual secondary meanings. If there's any doubt, check out the original poster art for the film:
http://en.wikipedia.org/wiki/File:ShaftBigScore.png

Slang is like obscenity, I can't necessarily define it very well but I know it when I hear it.

What, the heavy breathing, you mean?

Don't know much about obscenity, but I know what I like.

a private language of their own usable only within the family
In the Middle East it is taken for granted that a deaf child's family will have their own sign language for communicating with the child. Then if the child goes to a school for the deaf they learn standard Arabic sign language. Sometimes one person in the family also takes a class in signing.

"In the Middle East it is taken for granted that a deaf child's family will have their own sign language for communicating with the child. Then if the child goes to a school for the deaf they learn standard Arabic sign language."

That phenomenon is widely known throughout the world and is known as 'home sign'. Home sign systems, of course, aren't full languages but rather limited collections of ad hoc signs that arise in a particular family.

I really doubt there is a standard Arabic sign language used by deaf people. I know of no community of deaf people in the world interested in using a signed system based on a spoken language. Show me where the schools for the deaf are (and who founded them) and I could tell you more about the natural sign languages used by Arabs.

Michael, here's one:
http://www.jordanembassyus.org/10262001008.htm
This one is private; there are public ones too, for children. They use Jordanian Arabic; I was surprised to find out from a guy at a deaf social club in Amman that they often learn the Hebrew as well, as many Palestinians live in Israel.
I don't know all the differences between Arabic and English signing, but one of them is the question words. The Arabic uses the same circular motion around pursed lips for all the wh- words: who, what, where--while the English differentiates between the words with different motions around the lips. The school in the above link publishes a Jordanian Arabic sign dictionary.

AJP: Don't know much about obscenity, but I know what I like.
Kron is oddly quiet; I fear he has gotten into the Jul Akvavit. Shall we start posting hangover cures? Or glogg recipes?

Yes, I'm starting to worry about Kron. We used to have a bottle of glögg at the Hattery, but I think we threw it out a move or two ago, having realized we were never actually going to drink it.

I'm pretty sure that getting glögg out of a bottle is cheating. I was going to post glögg instructions last year, but never finished the draft--maybe I was wondering if it would mix with the Islamic stuff I write about. It's posted now.

"while the English differentiates between the words with different motions around the lips"

In ASL the non-manual feature that accompanies WH-questions is knitted eyebrows as opposed to the raised eyebrows of yes-no questions (there's a similar distribution in a number of other natural sign languages).
There is no "English" sign language. ASL and British sign language (BSL) are completely different, Irish sign language is distantly related to ASL (through Old French Sign language the Latin of European sign languages) and Australian and New Zealand sign languages are direct descendents from BSL (which has no relation to French Sign Language).
Canada has two sign languages Canadian ASL and QSL (quebec sign language though IINM the borders of the two don't completely correspond to provincial or linguistic boundaries)

The description of wh-words came up during a conversation with someone who had studied the Jordanian sign language and had frequent contact with educators and deaf students. If you look at this summary,
http://eric.ed.gov/ERICWebPortal/custom/portlets/recordDetails/detailmini.jsp?_nfpb=true&_&ERICExtSearch_SearchValue_0=EJ727757&ERICExtSearch_SearchType_0=no&accno=EJ727757
It looks to me like there is an Arabic alphabet for the deaf.
It also looks here:
http://books.google.com/books?id=8-9_MUQK0U4C&pg=PA103&lpg=PA103&dq=jordanian+sign+language&source=web&ots=Z3Lyr__wed&sig=EOUQYuDAhmOX-Xb62VmyMbWcrIQ#PPR5,M1
....like deaf people from different Arab countries can understand each other.
This list
http://www.ethnologue.com/show_family.asp?subid=90008
seems to recognize Jordanian.