slang for "drunk," 1736, sometimes said to be from notion of a ship heavy-laden and so low in the water that small waves (half seas) wash over the deck. This suits the sense, but the phrase is not recorded in this alleged literal sense. Half seas over "halfway across the sea" is recorded from 1550s, however, and it was given a figurative extension to "halfway through a matter" by 1690s. What drunkenness is halfway to is not clear.
1726, "a curious perversion" [Weekley] of Middle English heels over head (late 14c.) "somersault fashion," hence "recklessly." Head (n.) and heels long have been paired in alliterative phrases in English, and the whole image also was in classical Latin (per caput pedesque ire).
mid-14c., also simply coat (mid-14c.); originally a tunic embroidered or painted with heraldic armorial bearings (worn over armor, etc); see coat (n.) + arm (n.2) and compare Old French cote a armer. Sense transferred in Middle English to the heraldic arms themselves. Hence turncoat, one who put his coat on inside-out to hide the badge of his loyalty (1550s).
with year-dates, an occasional Roman method of identifying a given year by reference to the time passed since founding of the city, which in 1c. B.C.E. was calculated to have taken place in what we would call 753 B.C.E. Literally "from the city founded;" the elements are ab "from" (see ab-) + ablative of urbs "city" (see urban) + fem. past participle of condere "put together, store," from assimilated form of com- "together" (see com-) + -dere "put" (from PIE root *dhe- "to put, place").
legal Latin, "in the process of being done," from fieri "to come into being, become," used as passive of facere "to make, do" (from PIE root *dhe- "to set, put").