You can be raring to go, enjoy your meat rare, or have a rare crustacean collection. Is there a common root, or do they all have their own rare origins? Ironically, the latter. First, the one with a definition of "scarce": it comes from the Old French word rere, with the same meaning, from Latin rarus, meaning "spaced apart", since things that are spaced apart are rarer than those that are not, and that in turn is from Proto-Indo-European ere, which could have meant something like "separate" or "thin"- two definitions that can easily be connected to the prior meaning. Now onto the origins of your rare meat: the word is from Old English hrere, "lightly cooked", from hreran, "to agitate" (probably something to do with the cooking process). Prior to that, we can reconstruct it to Proto-Germanic hrorjan, "stir", and ultimately to PIE kera, "to mix". Last but not least, the word raring is an archaic form of rare, a dialectical way to say rear, the verb meaning "to raise", as in what you hopefully do to your child. Rear, through Old English and Proto-Germanic synonyms raeran and raizijana, originated from the Proto-Indo-European hrey, which meant something more like "to rise" than "to raise". Just thought that was whimsical and interesting...
Adam Aleksic, a rising sophomore studying linguistics and government at Harvard University, has been described as the internet's sixth most famous etymologist. He also has disturbing interests in politics, vexillology, geography, board games, conlanging, and law.