cuss (n.) Look up cuss at Dictionary.com
1775, American English dialectal, "troublesome person or animal," an alteration of curse (n.), or else a shortening of the slang sense of customer.
cuss (v.) Look up cuss at Dictionary.com
"to say bad words," 1815, alteration of curse (v.). Related: Cussed; cussing. To cuss out attested by 1881.