mid-14c. (c. 1200 as a surname), "crown or top of the head (including hair)," presumably from a Scandinavian source (though exact sense cognates are wanting) related to Old Norse skalli "a bald head," skalpr "sheath, scabbard," from PIE root *skel- (1) "to cut," which is also the base of shell, skull, and scallop.
French scalpe, German, Danish, Swedish skalp are from English. Meaning "head skin and hair cut or torn from the head as a victory trophy" is from c. 1600, in Holland's Pliny, 1670s in reference to some North American tribal customs; as proof of the killing of an animal by 1703. Figuratively, as a symbol of victory, by 1757.
1670s, "to deprive of the scalp, cut off (someone's) scalp," from scalp (n.), originally in reference to North American natives. For ticket re-selling sense, see scalper. Related: Scalped; scalping. Compare German skalpern, Danish skalpere, Swedish skalpera. French scalper is from Germanic. Similarity to Latin scalpere "to cut, carve" is accidental.