U.S. colloq. [I swow app. = Is vow (I shall vow); cf. SWAN v.2] I swow, I declare; = SWAN v.2
[1790. Mass. Spy, 30 Dec., 1/1. In one village you will hear the phrase I snore,in another, I swowgar,and in another, I van you, I wunt do it.]
1844. J. Slick, High Life N. York, I. 104. I swow, Miss Miles, you look as harnsome as a full blown rose this morning.
1872. Schele de Vere, Americanisms, 595. I swan, I swad, I swow, I swamp, and I vum, for I swear, and I vow.