c. 1300, "bondsman; common man, man of low birth," from Old Norse karl "man" (as opposed to "woman"), "male, freeman," from Proto-Germanic *karlon- (source also of Dutch karel "a fellow," Old High German karl "a man, husband"). The same Proto-Germanic source produced Old English ceorl "man of low degree" (see churl) and the masc. proper name Carl and, via French and Latin, Charles.
The Mellere was a stout carle for the nones [Chaucer]
1650s, from Late Latin sponsor "sponsor in baptism," in Latin "a surety, guarantee, bondsman," from sponsus, past participle of spondere "give assurance, promise solemnly," from Proto-Italic *spondejo- "to pledge," literally "to libate many times," from PIE *spondeio- "to libate" (source also of Hittite ishpanti- "to bring a fluid sacrifice, pour;" Greek spendein "make a drink offering," spondē "libation, offering of wine;" compare spondee). Sense of "person who pays for a radio (or, after 1947, TV) program" is first recorded 1931.