'auspicial' originates from Latin, specifically the word 'auspicium' (from 'auspex'), where 'aus-'/'avis' meant 'bird' and 'spec-'/'specere' meant 'to look or observe'.

'auspicial' developed via Late Latin and Medieval Latin forms related to 'auspicium' and from the noun and adjective family that produced English 'auspice' and 'auspicious'; the modern adjective was formed by adding the suffix '-al' to a stem related to 'auspice'.

Initially it referred specifically to practices or signs observed by watchers of birds (divination); over time it broadened to mean anything relating to auspices or, rarely, indicating a favorable omen.