cockroach

English borrowed this word from Spanish cucaracha, which came from cuca, a term for butterfly caterpillars of onomatopoeic origin, related to Greek kókkux and Late Latin cucus.

Once it entered English, cucaracha was reshaped by folk etymology — English speakers heard it and reworked it into the more familiar-sounding cock and roach, giving the insect its current name.

It's a doublet of Spanish cucaracha, meaning the two words share the same root but took different paths — one staying in Spanish, one twisted into English by cock and roach.