'ill-behaved' originates from English, specifically the elements 'ill' (meaning 'bad') and 'behave' (meaning 'to conduct oneself'). 「ill-behaved」は英語に由来し、要素は「ill」（『悪い』）と「behave」（『ふるまう・振る舞う』）である。

'behave' comes from the verb formed with the prefix 'be-' + 'have' (Old English 'habban'), and appeared in Middle/early Modern English as 'behave' or 'behaven' meaning 'to conduct oneself'. 'ill' descends from Old English 'yfel' (bad, evil) and Proto-Germanic *ubilaz. The compound 'ill-behaved' developed later as a hyphenated adjective in Modern English to describe bad conduct.

Initially, the components meant 'bad' (ill) and 'to conduct oneself' (behave); together they have long been used to mean 'conducting oneself badly', a meaning that has remained stable into modern usage.