Word Origin & History
O.E. swerian "take an oath" (class VI strong verb; past tense swor, pp. sworen), from P.Gmc. *swarjanan, from root *swar- (cf. O.S. swerian, O.N. sverja, Dan. sverge, O.Fris. swera, M.Du. swaren, O.H.G. swerien, Ger. schwören, Goth. swaren "to swear"), from PIE base *swer- "to speak, say" (cf.
O.C.S. svara "quarrel"). Also related to the second element in answer
. The secondary sense of "use bad language" (c.1430) developed from the notion of "invoke sacred names." Swear-word is Amer.Eng. colloquial from 1883. Swear off "desist as with a vow" is from 1898.