'baalism' originates from the Semitic word 'baʿal', where 'baʿal' meant 'lord'; the English noun was formed with the suffix '-ism' (from Greek '-ismos' via Latin/Old French) to denote the system of worship associated with that name.

'baalism' developed from Biblical Hebrew/Ugaritic 'baʿal' (borrowed into Greek and Latin renderings and then into Old French/Medieval Latin as 'Baal'), and finally entered modern English as 'Baal' with the productive suffix '-ism' yielding 'baalism'.

Initially it specifically meant 'worship of Baal', but over time it broadened to mean 'idolatry' or more generally 'pagan/false worship' and, metaphorically, excessive devotion to a false object.