'aprioristically' originates from Latin, specifically the phrase 'a priori', where 'a' meant 'from' and 'prior' (Latin 'prior') meant 'earlier'; the adjective-forming element '-istic' (from Modern Latin/French formation) and the English adverbial suffix '-ally' were added to form the modern English adverb.

'aprioristically' changed from the Latin phrase 'a priori' and the modern scholarly adjective 'aprioristic' (formed from that phrase), and eventually became the modern English adverb 'aprioristically'.

Initially it meant the literal sense 'from the earlier' (i.e., prior to experience), but over time it evolved into its current meaning 'in a manner based on reasoning or principles prior to empirical observation'.