'mindlessness' originates from English, specifically from the base word 'mind' plus the suffixes '-less' and '-ness'. 'mind' comes from Old English 'gemynd' meaning 'memory, thought'; the suffix '-less' comes from Old English '-lēas' meaning 'without'; and the suffix '-ness' comes from Old English '-nes(s)e' used to form nouns denoting a state or quality.

'mind' developed from Old English 'gemynd' to Middle English 'mind(e)' and then to modern English 'mind'. The adjective 'mindless' was formed by combining 'mind' + Old English-derived suffix '-less' (Middle English '-les'), and later the noun-forming suffix '-ness' was added (from Old English '-nes(s)e') to create 'mindlessness' in Modern English.

Originally the components conveyed 'without mind' or 'without memory/thought'; over time the combined word evolved to mean 'a lack of thought, attention, or consideration' in general contexts.