Pict (n.)
an ancient people of Great Britain, late 14c., 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. The Old English name for the people was Peohtas.
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.