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How to write “calf's liver” on menu
I'm trying to find out which of the terms calf's-foot jelly and calves'-foot jelly is more appropriate for referring to this aspic-like comestible in conversation, but haven't found any definitive answer; ngrams shows similar frequency of use for both terms. Any advice? 
Edit: I added suggested term calves'-feet jelly to the ngrams search. For brief intervals ca. 1810, 1840, and 1900, it was dominant, but usually one of the other two terms has prevailed in frequency.