grump (n.) Look up grump at Dictionary.com
"ill-humor," 1727, in humps and grumps "surly remarks," later the grumps "a fit of ill-humor" (1844), then "a person in ill humor" (1900); perhaps an extended sense of grum "morose, surly," which probably is related to Danish grum "cruel;" or perhaps suggested by grumble, grunt, etc.