Idiomatic items in speech are what make the learning of a new language so difficult.

ellipsis : the act of leaving out one or more words that are not necessary for a phrase to be understood

: a sign (such as . . .) used in printed text to show that words have been left out

I think the word you want is Metalepsis. It's a word or figure of speech used in a new (or shortened) context, in this case, it is a shortened version of something that is already a figure of speech (a synecdoche - "shell like ear" = you listen/talk to you).

Just a guess. And a pleasure to wander through some of the rhetorical terms I haven't used much since grad school.

SRS