Argthtjtr

Two of my favorite double contractions are "couldn't've" and "shouldn't've", both of which are flagged by my spell checker, but seem completely correct to me.

"Fish 'n' chips" and similar phrases with "'n'" technically have a double-contracted "and."

The example you give is not done in American English. You can't contract non-auxiliary "have". "I've not a clue if this is possible" is also not grammatical in American English. It may be in British English, though.

I copied this from a comment I left below, because I think it clarifies what I'm trying to say:

I've" is a fine contraction, just in American English you can only use it to replace "I have" when "have" is used as an auxiliary verb (e.g. in conjunction with a past participle). "I've been there" is OK. "I've a dog" is not. In the example "I'ven't a clue"—"I haven't a clue", the verb "have" is not auxiliary, so it can't be contracted with the pronoun "I".

I don't think you can get away with "I'ven't" in writing either. However, I think I've read "'tweren't," "'twouldn't," and "'twasn't" before. I'm guessing, though, that double contractions like that are never technically correct. Colloquially speaking, if you're understandable, anything goes.

I guess this isn't entirely formal standard English, but I'm pretty sure "y'all're," "y'all've," and "y'all'll" are accepted in areas that use "y'all" as the second person plural.

I wouldn't use I'ven't in speech or writing. I've not perhaps, I haven't more likely. I do use, in both speech and writing, I'd've. I'd've thought this would be more common.

I would avoid doing that in any serious writing, but if you are looking for ways to do this creatively to affect a regional dialect, etc. I would suspect any text by Mark Twain would be a good source to find examples of this.

See: 19th-century English: wo'n't and ca'n't

When you say "I've done it" it's pronounced something like [aiv donit] (with the stress on [ai]), but when you say "I haven't done it" it's pronounced something like [ai (h)avent donit] (with or without an h sound, with the stress on [av]). Since the initial "h" is very weak in English anyway it's superfluous to omit it with an apostrophe unless you're making a point about exactly how someone pronounced it.

If you're saying [ai hav donit] (with stress on [hav]), you should write it "I have done it", with or without the italics depending on how important the emphasis is.

(By the way, I'm not a native speaker, this is how I see it with my foreign eyes. I'm sure the phonetic spelling is all messed up, but I hope you understand it anyway...)

Nobody seems to have mentioned it, but what you'd be more likely to hear in British English is "I 'aven't".

As Steve Melnikoff commented, "I've not" is sometimes used in the UK, though his example reads strangely to me; I'd have suggested something like "I've not seen him before".

See also Apostrophes in contractions: shan't, sha'n't or sha'nt?.

I was looking into the example of sha'n't because I just ran across that spelling in Henry James's short story, "The Great Condition" (1900), where characters named Bertram Braddle and Henry Chilver converse as follows:

"A-ah!" Chilver murmered, as if only only now with a full view. "She means she'll speak when you are married."

"When we are. And then only on one great condition."

"How great?"

"Well, that if after six months I still want it very much. She argues, you know, that I sha'n't want it."

"You won't then—you won't!"cried Chilver with a laugh at the odd word and passing his arm into his friend's to make him walk again.

There are several striking things about this occurrence of sha'n't. First, in the many stories that James wrote between 1892 and 1900, the spelling with two apostrophes occurs only this once (I believe). Notably, James doesn't spell won't with two apostrophes one line later—and more to the point, he spelled shan't with one apostrophe earlier in the same story:

"Shan't I go with you to the station?" his companion [Chilver] asked.

And finally, Chilver is particularly struck by "the odd word," though he himself used shan't earlier. This suggests that James is using the double punctuation to indicate an unusual pronunciation of the word sha'n't (perhaps as two syllables: sha-ent?), much as he uses a hyphen to indicate an unusual pronunciation or drawing out of "A-ah!" at the beginning of the quoted dialogue.

In any event, it's clear that writers can and do sometimes use two apostrophes in a single contraction, just as they can and sometimes do compress multiple words into one (as in the case of whadya for "what do you") without using any punctuation to clarify what's going on.

Not sure if it counts, but o'clock is a contraction of "of the clock".