Meaning

noun implement consisting of a small piece of cotton that is used to apply medication or cleanse a wound or obtain a specimen of a secretion

noun cleaning implement consisting of absorbent material fastened to a handle; for cleaning floors

verb wash with a swab or a mop

originMid 17th century (in the sense 'mop for cleaning the decks'): back-formation from Middle English swabber (“sailor detailed to swab decks”), from Middle Dutch zwabber, from a Germanic base meaning 'splash' or 'sway', also found as nautical German Schwabber and Volga German Schwabber ("scrubber, mop, swab")

Etymology from Wiktionary, CC BY-SA 3.0