'unamidated' originates from the English negative prefix 'un-' (from Old English 'un-') combined with 'amidated'. 'Amidated' derives from the verb-forming use of 'amide' + the suffix '-ate', where 'amide' names the chemical group 'amide'.

'unamidated' was formed by prefixing 'un-' to 'amidated'. 'Amidated' comes from the verb 'amidate' (a formation from 'amide' + '-ate' in modern chemical nomenclature), so the sequence was 'amide' → 'amidate' → 'amidated' → 'unamidated'.

Initially the components referred specifically to the chemical group 'amide' and the action of forming an amide; the composed adjective has consistently meant 'not having been amidated' or 'lacking an amide group' in modern usage.