Wrapped or covered to deaden sound; speaking in a way that is unclear or difficult to hear.
From Middle English 'muffle,' possibly from Old French 'moufle' meaning mitten or thick glove. The sense evolved from covering something with cloth to deadening sound.
When you 'muffle' something, you're wrapping it like a mitten (the original meaning), which is why heavy blankets and thick clothing actually do muffle sound—wrapping dampens vibrations, turning sound energy into heat.
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