Old English deað "death, dying, cause of death," in plura, "ghosts," from Proto-Germanic *dauthaz (cf. Old Saxon doth, Old Frisian dath, Dutch dood, Old High German tod, German Tod, Old Norse dauði, Danish død, Swedish död, Gothic dauþas "death"), from verbal stem *dheu- (3) "to die" (see die (v.)) + *-thuz suffix indicating "act, process, condition."
Death's-head, a symbol of mortality, is from 1590s. Death row first recorded 1940s. Death knell is attested from 1814; death penalty from 1875; death rate from 1859. Slang be death on "be very good at" is from 1839. Death wish first recorded 1896. The death-watch beetle (1660s) inhabits houses, makes a ticking noise like a watch, and was superstitiously supposed to portend death.