Understand, as in Aunt Mary doesn't catch on to any jokes. The verb to catch alone was used with this meaning from Shakespeare's time, on being added in the late 1800s. Also see get it, def. 2.
Become popular, as in This new dance is really beginning to catch on. [Late 1800s]
Dictionary.com presents 366 FAQs, incorporating some of the frequently asked questions from the past with newer queries.