Verb
muffle up (third-person singular simple present muffles up, present participle muffling up, simple past and past participle muffled up)
(dated) to clothe; to wrap up in clothing
The people who hanged Christ never, to do them justice, accused him of being a bore - on the contrary, they thought him too dynamic to be safe. It has been left for later generations to muffle up that shattering personality and surround him with an atmosphere of tedium. Dorothy L. Sayers