What does the expression "sour mouth" mean? 口を酸っぱくして


> オレが口を酸っぱくして教えたよね？

To my understanding, it means "Did I teach you to do it with a sour mouth?" or
actually, "Didn't I teach you with a sour mouth?", but I'm not sure what sour
mouth means.




口を酸っぱくして教える means "tell [somebody something] over and over again [without any
effect]". 教える here is "tell" rather than "teach". A corresponding English
idiom would be "I've told you till I'm blue in the face!" I imagine the
underlying meaning is "I've said this so many times I've got a sour taste in
my mouth".

