(often + up) to wrap (somebody, oneself, or something) up so as to conceal, or protect, or keep warm (them, oneself, or it)
muffled themselves in the cocoon of middle-aged habit and convention — Aldous Huxley
to wrap or pad (something) to dull the sound it makes
to deaden the sound of (a gun, drum, hammer, etc)
to keep down or suppress (something)
muffled laughter
to prevent (somebody) from expressing something
(+ up) to wrap up for warmth or protection
[Middle English muflen, perhaps from early French moufle mitten]