It sounds like some people have an innately negative connotation of the word, perhaps in regard to it being an apt description of female genitalia; which is, of course, self lubricating… which begs the question if that stems from the demonization of all things vaginal.
And I agree with your buddies: the first thing that comes to mind is cake.
Potentially relevant given their attempt at explanation:
TLDR: the facial feedback hypothesis was recently tested for replication across 17 pre-registered studies. Average effect size was near 0 and pretty much none of the 17 studies reported a significant effect.
I never thought to ask myself but being a spanish speaker i can’t really think of a word that elicits a negative reaction in the same way that english speakers have to ■■■■■.
There might be one but nothing readily comes to mind.