mumchance
Mute, or not speaking; silent.
There is something exceedingly unpleasant in being obliged to answer "No," to a traveller's "Pray, Sir, were you ever abroad?" and to sit mum-chance all the time that he is running over the "grimoire" of outlandish technicalities. For my own part, I am convinced that man is, par excellence, a travelling animal; [...]
Where it comes from
From Middle English mommen (“mutter, be silent”) and Middle High German mummenschantze (“game of chance as part of a masquerade, mime performance, revel”), from Old French momen (“mask”) and chance (“game of chance”).
Adapted from the Wiktionary entry mumchance (CC BY-SA 4.0).