'asst' is an abbreviation of 'assistant'. 'assistant' originates from Latin, specifically the word 'assistens' (present participle of 'assistere' / 'adsistere'), where the prefix 'ad-' meant 'to' and 'sistere' (from 'stare') meant 'to stand'.

'assistant' passed into Old French as 'assistant' and Middle English retained forms from Old French before becoming the modern English word 'assistant' (and later shortened in writing and speech to abbreviations such as 'asst' or 'asst.').

Initially related to the idea of 'standing by' or 'being present' (literally 'one who stands by'), it evolved to mean a person who helps or supports another in a job or function; the abbreviation 'asst' preserves that modern meaning.