'atrichous' originates from Greek roots, specifically the prefix 'a-' (privative) and 'thrix' meaning 'hair', with the English adjective-forming suffix '-ous'.

'atrichous' was formed in New Latin/modern scientific usage by combining Greek elements 'a-' + 'thrix' and the adjectival suffix, and it entered English scientific vocabulary as 'atrichous'.

Initially it meant 'without hair', and over time the term was extended in biology to mean 'lacking flagella or cilia' in microorganisms and cells.