witness (n.) Look up witness at Dictionary.com
Old English witnes "attestation of fact, event, etc., from personal knowledge;" also "one who so testifies;" originally "knowledge, wit," formed from wit (n.) + -ness. Christian use (late 14c.) is as a literal translation of Greek martys (see martyr). Witness stand is recorded from 1853.
witness (v.) Look up witness at Dictionary.com
c.1300, from witness (n.). Related: Witnessed; witnessing.