What is the origin of phrase have thunk

The phrase "have thunk" is not a standard English phrase. It's likely a misspelling or mispronunciation of "have thought".

Here's why:

* "Thunk" is a sound word, usually describing a dull thud. It's not a verb that means "to think".

* "Thought" is the past tense and past participle of the verb "to think".

Therefore, "have thunk" is incorrect grammar and doesn't have a specific origin.

It's possible you've encountered this phrase in informal speech or in a humorous context where the speaker is intentionally using a misspelling or slang.