I'm sure we're all aware of the literal meaning of "for days", as in "I haven't seen him for days", or "after Christmas we'll have turkey curry for days".
However, I've heard, over the course of the last year or so, "for days" used to say that something is great, usually (but not always) with regard to physical attractiveness, for example "she's got abs for days". Another popular phrase is "legs for days" (definitely Urban Dictionary).
I've struggled to search on this, as most use of "for days" is related to the literal meaning.
How long has this usage been around? The UD entry is from 2007, so obviously for longer than I've been noticing it.
From what culture did it emerge?
Also there is a potential related meaning of "a lot of", for example in this tweet: "I have puns for days", but that could also mean marvellous, I'm not sure.
Again in this tweet: "got mix ups for days".
Is that a different meaning or the same?
NB: for a topical reference for all three meanings, the Twitter tag #fordays is a good place to start.
Best Answer
Green's Dictonary of Slang identifies two senses of "for days," the first is an exclamation that originated in the U.S. LGBT community.
The one citation under this sense is dated 1970.
The second sense seems to more closely apply to the description in the question referring to "a lot of" something. This sense is described by GDoS as hailing from U.S. black culture as early as 1968 and with an attestation from 2002.
The 2002 usage is typical:
Although GDoS treats these as two separate senses of the phrase with two separate cultural contexts, I think it is worth noting that there tends to be significant cultural exchange between the two communities, and I'm inclined to speculate that the term originated in one culture and drifted to the other. My interpretation of Green's entries and the note on the "original implication" is that he views the phrase as firmly rooted in LGBT culture.