'bacalao' originates from Spanish, specifically the word 'bacalao', where it ultimately derives from Portuguese 'bacalhau' (the Portuguese term for preserved cod).

'bacalao' changed from the Portuguese word 'bacalhau' into Spanish 'bacalao' and was later borrowed into English as the loanword 'bacalao' to refer to salted cod or dishes made from it.

Initially, it meant 'preserved (salted/dried) cod', and over time the word continued to refer to preserved cod while also coming to denote various regional dishes made from that fish.