'bacillariaceous' originates from New Latin, specifically the taxonomic name 'Bacillariaceae' (the diatom family), where 'Bacillaria' (a genus name within the group) derives from Latin 'bacillus' meaning 'little rod' and the suffix '-aceous' meant 'pertaining to'.

'bacillariaceous' was formed in modern scientific English by combining the New Latin family name 'Bacillariaceae' (from the genus 'Bacillaria') with the adjectival suffix '-aceous', producing the adjective 'bacillariaceous' used in descriptions of diatoms and related material.

Initially it referred specifically to things pertaining to the genus Bacillaria or the family Bacillariaceae (rod-like diatoms); over time it has come to be used more generally for characteristics or materials associated with diatoms.