A decal is a type of decorative design, but that word is actually a shortening of decalomania, which is the process of putting decorative designs onto things. This comes from the French word decalcomanie, with the same meaning. Eliminate the -manie suffix, and we're left with the word decalquer, which meant "to transfer" or "trace". Eliminate the de- prefix, and now we have calquer, a verb meaning "to imitate" (so the de- was a bit redundant). This is from Italian calcare, or "to press", and that comes, through a Latin cognate, from the noun calx, meaning "heel" (because heels press when you stomp on something). If you'll remember from four blog posts ago, this is also the origin of calque, which is quite interesting. As we've already discussed there, calx is from a Pre-Greek origin which is obscure to us. In a bizarre plot twist, it is likely that the word cockamamie comes from decalomania, because that actually once referred to decals before it was taken on as a word for something ridiculous later on.
Adam Aleksic, a freshman studying linguistics at Harvard University, has been described as the internet's sixth most famous etymologist. He has disturbing interests in words, vexillology, geography, board games, limericks, and law, and he loves writing about himself in the third person.
The Etymology Nerd