Old English steorfan "to die" (past tense stearf, past participle storfen), literally "become stiff," from Proto-Germanic *sterbanan "be stiff, starve" (source also of Old Frisian sterva, Old Saxon sterban, Dutch sterven, Old High German sterban "to die," Old Norse stjarfi "tetanus"), from extended form of PIE root *ster- (1) "stiff."
The conjugation became weak in English by 16c. The sense narrowed to "die of cold" (14c.); transitive meaning "to kill with hunger" is first recorded 1520s (earlier to starve of hunger, early 12c.). Intransitive sense of "to die of hunger" dates from 1570s. German cognate sterben retains the original sense of the word, but the English has come so far from its origins that starve to death (1910) is now common.