filter (n.) Look up filter at Dictionary.com
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.) Look up filter at Dictionary.com
1570s, from Medieval Latin filtrare, from filtrum (see filter (n.)). The figurative sense is from 1830. Related: Filtered; filtering.