Mum's the word Mum's the word Mum's the word is a popular English idiom. It is related to an expression used by William Shakespeare, in "Henry VI, Part 2". The word “mum” is a slanged version of momme, which was used between 1350-1400 in Middle English with very close to the same meaning: Be silent; Do not reveal "Mum's the word" means to keep silent or quiet. "Mum" is a Middle English word meaning 'silent', and may be derived from the "mummer" who acts without speaking. Note the similar English word "mime" (Old English "mīma", Latin "mimus") meaning silent actor or imitator. The
Old English grammar and its imperative and participle forms from "bēon". (Modern German had an analogous, but even more complicated, development for its verb "sein".) In late OE and ME, the form "earon"/"earun", from the Old Norse "erun", replaced bēoþ and sind (See also List of English words of Old Norse origin). Old English is an inflected language, and as such its nouns, pronouns, adjectives and determiners must be declined in order to serve a grammatical function. A set of declined forms of the same word pattern is called a declension. As in several other ancient Germanic languages, there are five major cases: