mum
Preserved but no longer current.
Era: ca. 1874 (Victorian)
Where it’s used:
Origin
British & Irish English
Sources & notes
Historical definition reproduced from Hotten’s The Slang Dictionary (1874, public domain; Project Gutenberg #42108, retrieved 2026-07-31). Reflects the attitudes of its era.
Common questions
What does “mum” mean?
"to keep MUM," to hold one’s peace. Hence "MUM’S the word,"—a phrase which implies to all hearers that the matter to which it refers must remain secret.
Is “mum” formal or informal?
No register label has been reviewed yet — treat it as neutral and check the usage notes above.