'often-used' is formed in modern English from the adverb 'often' and the past participle 'used' (from the verb 'use'). 'often' originates from Old English 'oft', where 'oft' meant 'frequently'; 'use' ultimately comes from Latin 'uti' (via Old French 'user') meaning 'to use'.

'often' developed from Old English 'oft' into Middle English 'often', and 'use' entered English via Old French 'user' from Latin 'uti'; the combination of the adverb and past participle produced adjective phrases like 'often used' and later the hyphenated form 'often-used' in compound modifiers.

Originally the parts meant 'frequently' ('often') and 'to use' ('use'); together they described that something is 'used frequently' — this core meaning has remained stable into modern usage.