'baronetised' originates from English, specifically the verb 'baronetise', which is formed from the noun 'baronet' plus the verb-forming suffix '-ize' (or '-ise').

'baronet' entered English in the early 17th century from Old French 'baronet', a diminutive of 'baron' (compare Italian 'baronetto'); English then formed the verb 'baronetize'/'baronetise' by adding the productive suffix '-ize'/'-ise', and the past/past-participle form became 'baronetised'.

Initially the root 'baronet' referred to a 'little baron' (a hereditary title below baron); over time the derived verb came to mean 'to confer the title of baronet on (someone)', which is its current sense.