Word mysteries are where words in languages that I know don’t correspond to each other at all despite those languages often sharing lexical histories. These words are both mystifying (why are they different?) and annoying (why must you be different?!).
Thinking about peanuts (ES cacahuetes, FR cacahuètes) gets me thinking about rubber for reasons that will (hopefully) become clear in a moment.
EN → rubber — a tough elastic polymeric substance made from the latex of a tropical plant or synthetically. ORIGIN mid 16th cent.: from the verb rub + -er. [The substance was rubbed against writing to erase it.]
ES → goma — Sustancia viscosa e incristalizable que naturalmente, o mediante incisiones, fluye de diversos vegetales y después de seca es soluble en agua e insoluble en el alcohol y el éter. [Viscous and uncrystalizable substance which, naturally or through cutting, flows from various plants and, after drying, is soluble in water and insoluble in alcohol or ether.] Del lat. vulg. gŭmma, del gr. κόμμι. [From the common Latin gŭmma, from the Greek κόμμι.]
FR → caoutchouc — Substance élastique, imperméable et résistante obtenue par coagulation du latex de certaines plantes, arbres ou lianes de la forêt équatoriale, en particulier de l’hevea brasiliensis. [Elastic, impermeable and resistant substance obtained through the coagulation of latex derived from certain plants, trees or creeping vines found in rain forests, particularly the Brasilian rubber tree. ORIGIN Quechua word for the same substance, kauchuk. The Quechua are indigenous South Americans, settled along the Andes and the Amazon River, home to rubber trees.
Caoutchouc is a word that I willfully mispronounce (as “ka-chew ka-chew”) because it amuses me but it makes French people think I’m an idiot. I’m okay with that.
Writing all this up reminds me that when I first started teaching English as a second language, one of the things that threw me was little kids asking for rubbers. I never really got over it. I’ve accepted many Britishisms in my life, but, as an American, a rubber will always be a condom, not an eraser.