deeryoudaoicibaDictYouDict[deer 词源字典]
deer: [OE] In Old English, dēor meant ‘animal’ in general, as opposed to ‘human being’ (as its modern Germanic relatives, German tier, Dutch dier, and Swedish djur, still do). Apparently connected forms in some other Indo-European languages, such as Lithuanian dusti ‘gasp’ and Church Slavonic dychati ‘breathe’, suggest that it comes via a prehistoric Germanic *deuzom from Indo-European *dheusóm, which meant ‘creature that breathes’ (English animal and Sanskrit prānin- ‘living creature’ have similar semantic origins).

Traces of specialization in meaning to ‘deer’ occur as early as the 9th century (although the main Old English word for ‘deer’ was heorot, source of modern English hart), and during the Middle English period it became firmly established, driving out ‘animal’ by the 15th century.
[deer etymology, deer origin, 英语词源]
deer (n.)youdaoicibaDictYouDict
Old English deor "animal, beast," from Proto-Germanic *deuzam, the general Germanic word for "animal" (as opposed to man), but often restricted to "wild animal" (cognates: Old Frisian diar, Dutch dier, Old Norse dyr, Old High German tior, German Tier "animal," Gothic dius "wild animal," also see reindeer), from PIE *dheusom "creature that breathes," from root *dheu- (1) "cloud, breath" (cognates: Lithuanian dusti "gasp," dvesti "gasp, perish;" Old Church Slavonic dychati "breathe").

For prehistoric sense development, compare Latin animal from anima "breath"). Sense specialization to a specific animal began in Old English (usual Old English for what we now call a deer was heorot; see hart), common by 15c., now complete. Probably via hunting, deer being the favorite animal of the chase (compare Sanskrit mrga- "wild animal," used especially for "deer"). Deer-lick is first attested 1778, in an American context.