late 14c., of planets, "appearing to move in the sky contrary to the usual direction," from Latin retrogradus "going back, moving backward," from retrogradi "move backward," from retro "backward, reverse" (see retro-) + gradi "to go, step" (from PIE root *ghredh- "to walk, go"). General sense of "tending to revert" is recorded from 1530s; that of "directed backward, in a direction contrary to the original motion" is from 1620s. .
mid-15c., propellen, "to drive away, expel," from Latin propellere "push forward, drive forward, drive forth; move, impel," from pro "forward" (see pro-) + pellere "to push, drive" (from PIE root *pel- (5) "to thrust, strike, drive"). Meaning "to drive onward, cause to move forward" is from 1650s. Related: Propelled; propelling.
[to sway, move backward and forward] Middle English rokken "rock (a cradle), cause to sway back and forth; rock (someone) in a cradle," from late Old English roccian "move a child gently to and fro" in a cradle, which is related to Old Norse rykkja "to pull, tear, move," Swedish rycka "to pull, pluck," Middle Dutch rucken, Old High German rucchan, German rücken "to move jerkily."
The earliest associations of the word were with slumber, rest, security. The sense of of "sway to and fro under some impact or stress" is from late 14c., especially of vessels in the waves (1510s); hence rock the boat in the figurative sense "stir up trouble" (1914). The sense of "swing to and fro in or as in a rocking chair" is by 1795.
"take up and move with a shovel," mid-15c., shovelen, from shovel (n.). Often especially "move or throw in large quantities hastily and inelegantly." Related: Shoveled; shoveling. Compare German schaufeln, verb from noun. Shoveler (also shovelard) as a kind of duck is from mid-15c.