'undulatory' originates from Latin, specifically the word 'undulatus', where 'unda' meant 'wave' and the suffix '-atus' indicated 'possessing' or 'characterized by'.

'undulatory' changed from the Late Latin/Latin verb and adjective forms such as 'undulare' / 'undulatus' and passed into English via Neo-Latin and the verb 'undulate' (17th century), eventually forming the adjective 'undulatory'.

Initially, it meant 'having waves or a wavy form', and over time it has retained that basic sense while also extending metaphorically to describe wave-like motion or patterns.