Anyway, I planned to go into the history of the letter C, but it turns out it’s a bit more complicated than I thought. I have to look up some stuff about the Roman Conquest and Greek and all that, so I decided to give myself another week on that and whip up something about compulsion and impulse. Because they have to be related, right?
Impulse first showed up in the early fifteenth century, shortly before its relative impel (urge, encourage). The former comes from the Latin impulsus—pressure, push against—and it is the past participle version of the latter’s origin word impellere, which means to drive/urge forward, push against. The prefix, im-, is from in- and means into, while pellere means push (shocker, right?). If you haven’t guessed already, pellere is the origin word of pulse, which means an impulse is a pulse into doing something.
Compulsion showed up at around the same time as impulse, but compel (take action as a result of pressure) showed up almost a century earlier. The first comes from the Latin compulsionem while the second comes from compellere…now that looks familiar. Yes, its stem is also pulse, or drive/urge. The prefix com- means together. Compulsion is to drive everything together, or to force it all forward. Basically, it’s a driving force.
What’s interesting is the psychological meaning the words took on. Impulse first started to mean “stimulus in the mind” in the 1640s, while compulsion (compulsion neurosis) was coined in a 1909 translation by A.A. Brill of work by Freud. The words probably took on those meanings because of their appropriate relations to the mental states. An impulse in the old sense of the word is a single driving push prompted by some outside force (you’re being pushed into doing something). Now, an impulse usually refers to an automatic reaction to something, like yanking your hand from a hot stove. You don’t think about it, you have no emotion about it, you just do it. Compulsion on the other hand, is more of a driving force without an outside stimulus, and you feel the compulsion because of some inner force, like you have to check the locks on every window before going to bed and you’ll feel great emotion if you don’t.
Perhaps it’s easier to say that compulsion or compel is being forced to do something, either by some inner or outer force. Impulse or impel is an urge towards doing something, but face it, you can burn your hand on the stove if you mentally decide to keep it there.