pushover (n.)

c. 1300, pushen, "to shove, move onward, strike with a thrusting motion, thrust forcibly against for the purpose of impelling," from Old French poulser (Modern French pousser), from Latin pulsare "to beat, strike, push," frequentative of pellere (past participle pulsus) "to push, drive, beat" (from PIE root *pel- (5) "to thrust, strike, drive").

Transitive meaning "urge, incite, press" is by 1570s; that of "promote, advance or extend by persistence or diligent effort" is from 1714; intransitive sense of "make one's way with force and persistence (against obstacles, etc.)" is by 1718. The meaning "approach a certain age" is from 1937. For palatization of -s-, OED compares brush (n.1); quash. Related: Pushed; pushing.

To push up daisies "be dead and buried" is from World War I, but variants with the same meaning date back to 1842.

"Pushing up the daisies now," said a soldier of his dead comrade. [The American Florist, vol. xlviii, March 31, 1917]

To push (someone) around "bully, browbeat, domineer" is by 1923. To push (one's) luck is from 1754. To push the envelope in the figurative sense is by late 1980s.

Old English ofer "beyond; above, in place or position higher than; upon; in; across, past; more than; on high," from Proto-Germanic *uberi (source also of Old Saxon obar, Old Frisian over, Old Norse yfir, Old High German ubar, German über, Gothic ufar "over, above"), from PIE root *uper "over."

As an adjective from Old English uffera. The senses of "past, done,  finished; through the whole extent, from beginning to end" are attested from late 14c. The sense of "so as to cover the whole surface" is from c. 1400. Meaning "leaning forward and down" is from 1540s. The meaning "recovered from" is from 1929. In radio communication, it is used to indicate the speaker has finished speaking (1926).

Above expresses greater elevation, but not necessarily in or near a perpendicular direction; over expresses perpendicularity or something near it: thus, one cloud may be above another, without being over it. Over often implies motion or extension where above would not; hence the difference in sense of the flying of a bird over or above a house, the hanging of a branch over or above a wall. In such uses over seems to represent greater nearness. [Century Dictionary]

Phrase over and above (mid-15c.) is pleonastic, for emphasis. Adjective phrase over-the-counter is attested from 1875, originally of stocks and shares. To be (someone) all over "be exactly what one expects of (someone)" is by 1721.