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.
