I was just reading about what a whip is in the US Senate here. It got me wondering, why is it called a whip? It seems like an odd name to me when it could have just been called like 'leader' or 'speaker' or something more descriptive. I'm guessing that the term whip could have meant something to the average person back in the day that no one says anymore.
Apparently it comes from "whipper-in" which meant keeping the dogs from straying in a fox chase. So the idea is that the whip keeps the party members from straying... in their voting... at least in the British interpretation of that function. According to one newspaper
The formal title of the British parliamentary “whippers-in” was shortened to just “whip” in the 1840s.
Their roles, however, remained similar, that is, to ensure that the MPs in their party behaved as a single horde and not run off in their own directions trying to be independent or “vote according to their conscience”.
I managed to find again where I read some this (on senate.gov), which also discusses the alternate tiles for roughly the same job in the US, as well as the somewhat different (more limited) job function of the whip in the US:
The term "whip" comes from a fox-hunting expression— "whipper-in"—referring to the member of the hunting team responsible for keeping the dogs from straying from the team during a chase. Established early in the 20th century, the development of party whips coincided with the evolution of party leaders in the Senate.
Democrat James Hamilton Lewis of Illinois became the first party whip in 1913, and the Republicans established their own whip position two years later. Traditionally serving as assistant leaders, whips are mainly responsible for counting heads and rounding up party members for votes and quorum calls, and they occasionally stand in for the majority or minority leaders in their absence. In 1970 Republicans began referring to their whips as assistant leaders, but in 2003, they began using the whip title again. Democrats used the title whip until 2003, when they began calling the position assistant leader. In 2017 Democrats created a new position of assistant leader, which is separate from and ranks directly below the position of whip.