hart (n.)

Middle English hert, from Old English heorot "hart, stag, male of the red deer," from Proto-Germanic *herutaz (source also of Old Saxon hirot, Old Frisian and Dutch hert "stag, deer," Old High German hiruz, Old Norse hjörtr, German Hirsch "deer, stag, hart"), perhaps from PIE *keru-, extended form of root *ker- (1) "horn; head." For vowel change, see marsh.

In later times, a male deer after its fifth year, when the crown antler has appeared. The female is a hind (n.).