Merriam-Webster's Collegiate® Dictionary, 11th Edition
SWEAR
I. verb (swore; sworn; swearing)
Etymology: Middle English sweren, from Old English swerian; akin to Old High German swerien to swear and perhaps to Old Church Slavic svarŭ quarrel Date: before 12th century transitive verb to utter or take solemnly (an oath),
2. to assert as true or promise under oath , to assert or promise emphatically or earnestly ,
3. to put to an oath ; administer an oath to, to bind by an oath , to invoke the name of (a sacred being) in an oath, to bring into a specified state by swearing , intransitive verb to take an oath, to use profane or obscene language ; curse , swearer noun
II. noun
Date: 14th century
oath , swearword