Old English east, eastan (adj., adv.) "east, easterly, eastward;" easte (n.), from Proto-Germanic *aust- "east," literally "toward the sunrise" (source also of Old Frisian ast "east," aster "eastward," Dutch oost Old Saxon ost, Old High German ostan, German Ost, Old Norse austr "from the east"), from PIE root *aus- (1) "to shine," especially of the dawn. The east is the direction in which dawn breaks. For theory of shift in the geographical sense in Latin, see austral.
As one of the four cardinal points of the compass, from c. 1200. Meaning "the eastern part of the world" (from Europe) is from c. 1300. Cold War use of East for "communist states" first recorded 1951. French est, Spanish este are borrowings from Middle English, originally nautical. The east wind in Biblical Palestine was scorching and destructive (as in Ezekiel xvii.10); in New England it is bleak, wet, unhealthful. East End of London so called by 1846; East Side of Manhattan so called from 1871; East Indies (India and Southeast Asia) so called 1590s to distinguish them from the West Indies.
"middle; being the middle part or midst; being between, intermediate," Old English mid, midd from Proto-Germanic *medja- (source also of Old Norse miðr, Old Saxon middi, Old Frisian midde, Middle Dutch mydde, Old High German mitti, German mitte, Gothic midjis "mid, middle"), from PIE root *medhyo- "middle."
By late Middle English probably felt as a prefix only, and now surviving in English only as a prefix (mid-air, midstream, etc.). Prefixed to months, seasons, etc. from late Old English. As a preposition, "in the middle of, amid" (c. 1400) it is from in midde or a shortened form of amid (compare midshipman) and sometimes is written 'mid.
"with," a preposition formerly in common use but now entirely superseded by with (except in the compound midwife) from Old English mid "with, in conjunction with, in company with, together with, among, at the same time as," and in part from cognate Old Norse mið, from Proto-Germanic *medthi- (source also of Old Saxon mid, Old Frisian mith "together with, with the help of," Dutch met, Old High German and German mit, Danish med, Gothic miþ "with"), from PIE *meti-, suffixed form of root *me- "in the middle" (compare meta-).