- filter (n.)
- early 15c., from Old French filtre and directly from Medieval Latin filtrum "felt," which was used to strain impurities from liquid, from West Germanic *filtiz (see felt (n.)). Of cigarettes, from 1908.
- filter (v.)
- 1570s, from Medieval Latin filtrare, from filtrum (see filter (n.)). The figurative sense is from 1830. Related: Filtered; filtering.