Definition: a silent stupid person
Mumchance has a rich palette of uses to choose from. In addition to the noun sense above (and it can also refer to an old dice game) it may function as an adjective (“silent”), adverb (“silently”), and, most usefully, as a verb (“to be silent out of caution or stupidity”).
To all such, allow me to say, shame on you! for a pack of mumchances. What on earth are you good for? Think you that magazine writing—or stage-coach conversation is to be made up of axioms and apothegms, of essays and homilies? No.
— The Raleigh Register (Raleigh, NC), 12 Mar. 1853