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- (cognates: Gothic tunþus "tooth"), from an extended form of PIE *dent-, the root of tooth. But "there are no certain cognates outside of the Anglo-Frisian area" [OED].