means A whisker is one of the long, stiff sensory hairs that grow near the mouth and eyes of many mammals, or by extension a very small margin (as in 'won by a whisker').

from From Middle English 'wisker,' meaning something that whisks or sweeps — built on the verb 'whisk,' itself likely from a Scandinavian source (compare Old Norse 'visk,' a wisp or bundle). Originally a 'whisker' was simply a thing that whisks; by the 1600s the word had settled onto the bristly hairs that sweep across a face, and the sense of 'a hair's breadth' followed naturally.