'transient' originates from Latin, specifically the word 'transiens' (present participle of 'transire'), where 'trans-' meant 'across' and 'ire' meant 'to go'.

'transiens' (Latin) passed into Late Latin and then into English via French and Middle English forms; the modern English 'transient' appeared in the 17th century, and 'transiently' is formed by adding the adverbial suffix '-ly' to the adjective.

Initially, it literally meant 'going across' or 'passing over'; over time it took on the figurative sense of 'passing quickly' or 'temporary,' which is its current meaning.