'bacalao' originates from Spanish, ultimately influenced by Portuguese 'bacalhau' and likely from Medieval Latin form 'bacalārium' (exact ultimate origin uncertain).

'bacalao' was influenced by Portuguese 'bacalhau' (and related medieval Romance forms such as 'bacalārium') and entered modern Spanish; culinary use of the term spread into English from Iberian languages.

Initially it referred to the fish 'cod' (often salted or dried); over time it retained that core meaning and also broadened to denote specific traditional dishes made from salted cod.