Old English snod "ribbon for the hair," from Proto-Germanic *snodo (source also of Swedish snod "string, cord"), from PIE root *(s)ne- "to spin, sew" (source also of Lettish snate "a linen cover," Old Irish snathe "thread;" see needle (n.)). In the Middle Ages, typically worn by young unmarried girls, hence "It was held to be emblematic of maidenhood or virginity" [Century Dictionary]. Modern fashion meaning "bag-like hair net" first recorded 1938 (these also were worn by girls in the Middle Ages, but they are not snoods properly).
