I assume those who thrown up their hands at “bicep” are similarly exercised by “cherry” and “pea” … if not, why not?
It’s only a question of time. As Simon Horobin observed:
“The word cherry originates in the northern French dialect word cherise (a variant of the standard modern French cerise), which was adopted into English after the Norman Conquest of 1066.
Because it ended in an “s”, English speakers mistakenly understood it to be a plural form and so the false singular cherry was born. The same process lies behind the word pea, erroneously derived from the singular form pease (ultimately from Greek pison) – preserved in the nursery rhyme “pease pudding hot, pease pudding cold”.
Although these changes took place hundreds of years ago, the process can be observed today in the emergence of bicep: a singular form of biceps…”