Prefixes are fascinating. Attaching different ones can make a word for continue into a word for taking something upon oneself. Or the act of devouring. There’s also presume, which is a synonym for assume that is attached to what the person actually believes rather than based on evidence (as in, I assume this is a cat because it has four legs and meows; I presume this is a horse because despite looking like a cat, she gallops through the house). There’s also a great list of –sume words that I’ve never heard of, including desume, introsume, transume, subsume, absume and insume. Awesome points for anyone who can work one of those into a sentence that doesn’t seem contrived.
First on the list of –sume words that we’ve heard of is assume, which showed up in the early fifteenth century as assumpten and meant being taken up into heaven. Strange? Actually, not so much. Assume comes from the classical Latin assumere, a combination of a—from the prefix ad-, meaning towards—and sumere—take up. Together, that’s “to take up or towards oneself.” The “suppose” meaning of the word evolved in the sixteenth century, with the “take on” meaning coming a little later. When you assume, you could say you take it upon yourself to analyze the available evidence and answer a question. It’s still quite different from the original meaning, though.
Resume appeared around the same time, taken from the classical Latin resumere. The prefix re- of course means again. With –sumere, you have “to take up again,” which is pretty much what it means now. By the way, yes, résumé does come from resumere, however the French word was taken to mean a career summary much later, in the 1940s.
It’s worth noting that sumere itself is a prefixed word. It is su- (from sub-, as in under) + -emere, Latin for “purchase or take” and the origin word of exempt, among others. The sub- prefix was probably added to distinguish the meanings of the words. Like, say, assume from presume. (Segue, ho!)
Presume showed up a little after the first two (although presumption showed up two centuries earlier, along with assumption). Its original meaning was “to take upon oneself,” usually with an air of overconfidence. The overconfidence bit comes from presumption’s origin word, the late Latin praesumptionem, which meant confidence. Presume can be distinguished from assume because the former is grounded in belief. You are confident this is so, but you may not have the evidence to back it up. In classical Latin, the word is praesumere, with the prae- prefix meaning before. You take it up before. Before what? Before you really know.
Finally for -sume words we've actually heard of, we have consume, also from the late fourteenth century. It comes from the classical Latin consumere, with the con- prefix from com-, in this case used as an intensifier. The literal meaning would be “to take up” but consume has always meant “to use up.” This slight difference is probably more do to how we in English use the word take. When you take something up, it’s considered still in existence. Using something up, however, is eliminating it. By turning it into something else, but it’s still gone. So we are taking it, but in doing so are eliminating it from existence.
This is the kind of stuff that happens when you take words from other languages. Each language uses them in their own way and they become completely different from their original meaning. In five hundred years, words like tsunami and poltergeist will be unrecognizable (along with the rest of the English language, for that matter, but that's a story for another day).