darn (interj.)

tame curse word, 1781, American English euphemism for damn, said to have originated in New England when swearing was a punishable offense; if so, its spread was probably influenced by 'tarnal, short for Eternal, as in By the Eternal (God), favorite exclamation of Andrew Jackson, among others (see tarnation). Related: darned (past-participle adjective, 1806); darndest (superlative, 1844).

darn (v.)

"to mend" c. 1600, perhaps from Middle French darner "mend," from darne "piece," from Breton darn "piece, fragment, part." Alternative etymology is from obsolete dern (see dern). Related: Darned; darning.