As nouns the difference between grump and gump
is that grump is a habitually grumpy or complaining person while gump is (dated) a dunce, a foolish person or nitwit.
As a verb grump
is to complain.
grump
English
Noun
(
en noun)
a habitually grumpy or complaining person
First used in print by Daniel Defoe in 1727.
Verb
(
en verb)
to complain
to be grumpy
gump
English
Noun
(
en noun)
(dated) a dunce, a foolish person or nitwit