Old English weosule, wesle "weasel," from Proto-Germanic *wisulon (cf. Old Norse visla, Middle Dutch wesel, Dutch wezel, Old High German wisula, German Wiesel), probably related to Proto-Germanic *wisand- "bison" (see bison), with a base sense of "stinking animal," because both animals have a foul, musky smell (cf. Latin vissio "stench"). A John Wesilheued ("John Weaselhead") turns up on the Lincolnshire Assize Rolls for 1384, but the name seems not to have endured, for some reason.
"to deprive (a word or phrase) of its meaning," 1900, from weasel (n.); so used because the weasel sucks out the contents of eggs, leaving the shell intact; the sense of "extricate oneself (from a difficult place) like a weasel" is first recorded 1925; that of "to evade and equivocate" is from 1956.
: Little Joe turned weasel
verb[the first verb sense is said to be based on the weasel's habit of sucking the meat or substance from an egg, leaving only the shell; the other senses reflect the more general nasty reputation of the weasel, which has meant ''contemptible person'' since at least the 1500s]
jargon, abuse
(Cambridge) A naive user, one who deliberately or accidentally does things that are stupid or ill-advised. Roughly synonymous with loser.
[Jargon File]
(1995-03-21)
(Heb. holedh), enumerated among unclean animals (Lev. 11:29). Some think that this Hebrew word rather denotes the mole (Spalax typhlus) common in Palestine. There is no sufficient reason, however, to depart from the usual translation. The weasel tribe are common also in Palestine.