Merriam-Webster's Collegiate® Dictionary, 11th Edition
SWAB
I. noun
Etymology: probably from obsolete Dutch swabbe; akin to Low German swabber mop
Date: 1653
1. mop , b. a wad of absorbent material usually wound around one end of a small stick and used especially for applying medication or for removing material from an area, a specimen taken with a swab, a sponge or cloth patch attached to a long handle and used to clean the bore of a firearm,
2. a useless or contemptible person, sailor , gob ,
II. transitive verb (swabbed; swabbing)
Etymology: back-formation from swabber
Date: 1719
to clean with or as if with a swab, to apply medication to with a swab