dandruff n.

"scurf which forms on the scalp or skin of the head and comes off in small scales or dust," 1540s; the first element is obscure (despite much speculation, OED concludes "nothing satisfactory has been suggested"). The second element probably is Northumbrian or East Anglian dialectal huff, hurf "scab," from Old Norse hrufa, from Proto-Germanic *hreufaz, source of Old English hreofla "leper." Middle English words for it were bran (late 14c.), furfur (c. 1400, from Latin), scales (mid-15c.).