Although the word “Mum” came into vogue in Britain in 1823 as a term of endearment for one’s mother, this is not the “mum” that’s meant in the phrase “mum’s the word.” Mum is a word from the late 14th century, between 1350 and 1400, that means “silence.”
The origins of the phrase can be traced back to the fifteenth century Towneley Plays performed from the late Middle Ages until 1576. These plays are a series of 32 mystery plays based on the Bible and the Towneley Plays are but one of only four surviving English mystery play cycles that were written by multiple authors over the course of approximately two centuries. It is in these plays that one can find the phrase written thus:
“Though thi lyppis be stokyn, yit myght thou say ‘mum’.”
And, of course, what phrase from England from that time period could escape being included in some form or other in a play from Shakespeare? Yes, in Henry VI the sense of the phrase is found in Part 2, Act 1, Scene 2 when Hume says:
“Seal up your lips, and give no words but mum:
The business asketh silent secrecy.”
Yes, it’s obvious that in 1594, the playwright also believe that “mum” was the word without a doubt. Interestingly enough, the exact phrase “mum’s the word” became wildly popular over a hundred years after Shakespeare‘s play, in the 1700s and although still used today, it is not as popular a phrase as it once was.
Historically Speaking 