1812 as both a noun and verb, American English, from Elbridge Gerry + (sala)mander. Gerry, governor of Massachusetts, was lampooned when his party redistricted the state in a blatant bid to preserve an Antifederalist majority. One Essex County district resembled a salamander, and a newspaper editor dubbed it Gerrymander. Related: Gerrymandered; gerrymandering.
To change the boundaries of legislative districts to favor one party over another. Typically, the dominant party in a state legislature (which is responsible for drawing the boundaries of congressional districts) will try to concentrate the opposing party's strength in as few districts as possible, while giving itself likely majorities in as many districts as possible.