One of the people I went to university with had a little (very short) mental catalogue of "chromatic mathematical fruit jokes". There are exactly two famous ones. "What's purple and commutes?" "An abelian grape." And: "What's yellow and equivalent to the axiom of choice?" "Zorn's lemon." He invented another, which requires more esoteric knowledge: "What's green and determined up to isomorphism by its first Chern class?" "A lime bundle." I don't remember whether anyone found a credible fourth example.
(Oh, how we laughed.)
[In case anyone reading this thinks the above might be amusing if only they knew what mathematical objects were actually being referred to: (1) No, probably not. (2) Abelian group; Zorn's lemma; line bundle. For the last one, you need to make it the first Stiefel-Whitney class if you're working over the real numbers rather than the complex numbers.]
I vaguely remember a joke about limit of the supremum (lim sup) involving lime soup. In fact, I brought some lime soup into math class one day in undergrad. It tasted awful. And I can't remember the joke.
Nice! Except it doesn't quite work for me because the vowel sounds don't match. (For me the second and third "a"s in "banana" are like the "a" in "arm", whereas the two in "Banach" are like the "a" in "at", and those are quite different sounds. Other people may differ -- and indeed I may be mispronouncing "Banach".)
Whoops. Mine's the same. Two schwas and one a-as-in-arm.
[EDITED to add: Er, except that the first vowel in my "umbrella" isn't the same as I think you're putting in yours. In IPA, my umbrella is /ʌmbrɛlə/ and my banana is /bənɑːnə/, unless I've made mistakes there.]
As an American, I'll never understand how the English can indiscriminately throw /ɑː/'s into perfectly normal words, yet when faced with a foreign import that actually asks for it, willfully refuse.
Maybe I made more than one mistake in my description (I definitely made one: the third "a" in "banana" is of course a schwa, not the vowel in "arm") -- but the "a"s I put in "Banach" are (modulo incompetence) pretty much exactly the ones you'll find by clicking the "listen" link after Banach's name at the start of his Wikipedia page. So I'm not sure what you mean about "a foreign import that actually asks for it". And I just checked the etymology of "banana", and the likely Wolof original has exactly one /ɑː/ in it, in the same place as I put one. But, see above, I misdescribed how I say "banana" so I may have caused confusion.
(Oh, how we laughed.)
[In case anyone reading this thinks the above might be amusing if only they knew what mathematical objects were actually being referred to: (1) No, probably not. (2) Abelian group; Zorn's lemma; line bundle. For the last one, you need to make it the first Stiefel-Whitney class if you're working over the real numbers rather than the complex numbers.]