'inappropriately-combined' is a modern English compound formed from 'inappropriately' + 'combined'. 'inappropriately' ultimately derives from Latin elements: the prefix 'in-' (from Latin 'in-' meaning 'not') plus 'appropriate', which comes from Latin 'appropriare' (ad- + 'proprius') meaning 'to make one's own' or 'suitable'. 'combined' comes from Latin 'combinare' via Old French 'combiner', where 'com-' meant 'together'.

'appropriate' entered English via Late Latin and Old French, becoming Middle English 'appropriate'; the negative prefix 'in-' was added in English to form 'inappropriate' in the modern period. 'combine' came into English from Old French 'combiner', itself from Latin 'combinare'. The compound adjective 'inappropriately-combined' is a descriptive formation in modern English combining an adverb + past participle.

Originally, the elements meant 'not suitable' (in- + appropriate) and 'to join together' (combine). Over time they combined into a descriptive phrase meaning 'joined together in an unsuitable or incorrect way', which is the current usage.