Frisian (adj.)
"of or pertaining to the people of Frisia," or "belonging to the tribe of the Frisii," 1590s, from Latin Frisii, from a Germanic tribal name (source also of Old Frisian Frise, Middle Dutch Vriese, Old High German Friaso, Old English Frisa), perhaps originally meaning "curly-headed" (compare Old Frisian frisle "curly hair"). As a noun, "West Germanic language spoken in Friesland," the lowland coast of the North Sea and nearby islands, closely related to Dutch and Old English.