tusk (n.) Look up tusk at Dictionary.com
Old English tusc, also transposed as tux, "long, pointed tooth protruding from the mouth of an animal," cognate with Old Frisian tusk, probably from Proto-Germanic *tunthsk- (source also of Gothic tunþus "tooth"), from an extended form of PIE root *dent- "tooth." But "there are no certain cognates outside of the Anglo-Frisian area" [OED].