one of an ancient people formerly inhabiting the Highlands of Scotland and other parts of the British Isles beyond the reach of the Romans, late 14c. (replacing Old English plural Peohtas), from Late Latin Picti (late 3c., probably a nickname given them by Roman soldiers), usually taken as derived from picti "painted," but probably ultimately from the Celtic name of the tribe, perhaps Pehta, Peihta, literally "the fighters" (compare Gaulish Pictavi, a different people, who gave the name to the French city of Poitiers). They painted and tattooed themselves, which may have suggested a Roman folk-etymology alteration of the name.
In Scottish folk-lore, the Pechts are often represented as a dark pygmy race, or an underground people; and sometimes identified with elves, brownies, or fairies. [OED]
Related: Pictish; Pictland.