"Keeping mum" may be a reference to the wax used to prepare Egyptian mummies for burial. “Mum” appears to be a word of imitative origins, referencing the “mmmmmm” sound that people make when their mouths are closed and they try to talk, or when someone tries to talk with a hand clamped over his or her mouth.
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 an alteration of momme, which was used between 1350 and 1400 in Middle English with very close to the same meaning, "be silent; do not reveal".
The word “mom”, on the other hand, is a slightly different story and it's widely believed that the word was born from the much older word “mamma” which itself can be traced back to the 1500s in English. This, in turn, can be traced back to Latin where “mamma” meant “breast” or “teat”.
This World War II poster urges British officers and other servicemen to"keep mum" (quiet), lest military secrets and other sensitive information fall into the hands of the enemy as a result of careless talk, in this case overheard by a beautiful female spy.
Mum can be a noun or an adjective. As an adjective, mum is a synonym of silent, like in the phrase mum's the word. As a noun, mum has two meanings. A mum is a type of flower often grown for decorative purposes.
"We are born of love; Love is our mother." "When you look into your mother's eyes, you know that is the purest love you can find on this earth." "A mother is she who can take the place of all others but whose place no one else can take." "Life doesn't come with a manual, it comes with a mother."
What you are hearing is not mum as in mother, but ma'am, contraction of madam, with a strongly reduced vowel. In British English, it is mostly used as a sign of repect for a woman of superior rank, say, in the military or police.
1 : to not show or express (something, such as an emotion) You shouldn't keep your anger in all the time. 2 : to continue to provide (someone) with (something needed or wanted) It's very expensive keeping my children in clothes that fit.