grumble (v.) Look up grumble at
1580s, "complain in a low voice;" 1590s, "make a low, rumbling sound," from Middle French grommeler "mutter between the teeth" or directly from Middle Dutch grommelen "murmur, mutter, grunt," from grommen "to rumble, growl." Imitative, or perhaps akin to grim (adj.). With excrescent -b- as in mumble. Related: Grumbled; grumbling.
grumble (n.) Look up grumble at
1620s, from grumble (v.).