Reverser

Part of speech: noun

Definitions

1. A person or device that causes something to move or operate in the opposite direction
2. One who changes the order or direction of something to its contrary state
3. An agent or tool that brings about the reversal or backward movement of an action or condition

Etymology: "Reverser" is a simple formation: the verb "reverse" with the agent suffix "-er" attached, so it names whatever or whoever does the reversing. The suffix has a longer pedigree than the word it sits on. It descends from Latin "-arius", which passed through Old French "-ier" and reached English as Middle English "-er". Old English had its own version, "-ere", which is why the ending became so common in ordinary English nouns. The verb "reverse" is the more interesting half. It was borrowed from Old French "reverser", which came from Latin "revertere", meaning "to turn back". The Latin prefix "re-" gives the sense of backward movement, and the verb carried that literal turning-around into English before it took on the wider senses of changing direction or undoing a decision. Adding "-er" to it produced a noun for the agent, such as a mechanism that runs a gear backwards.

Synonyms: reversal, inverter, converter, switch, flipper