Merriam-Webster's Collegiate® Dictionary, 11th Edition
MUZZLE
I. noun
Etymology: Middle English mosel, from Middle French musel, from Old French *mus mouth of an animal, from Medieval Latin musus
Date: 15th century
the projecting jaws and nose of an animal ; snout ,
2. a fastening or covering for the mouth of an animal used to prevent eating or biting, something (as censorship) that restrains normal expression, the open end of an implement,
II. transitive verb (muzzled; muzzling)
Date: 15th century
to fit with a muzzle,
2. gag , restrain , restrict , muzzler noun