Crossword puzzles flex one very specific piece of cognition--the ability to find words, which is also known as fluency. Fluency is a type of process based in the speech and language centers of the brain. So doing crosswords might help you get better at word finding, but that's the sum total of their positive benefits to your brain.
misnomer. n. 1. an incorrect or unsuitable name or term for a person or thing. 2. the act of referring to a person by the wrong name.
1. a word or phrase apparently modifying an unintended word because of its placement in a sentence: e.g., 'when young' in 'when young, circuses appeal to all of us'. Familiarity information: MISPLACED MODIFIER used as a noun is very rare.