1
general::
1. 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. 2. Be come popular, as in This new dance is really beginning to catch on. [Late 1800s]
American Heritage Idioms
2
general::
Phrase(s): catch something on something
to snag something on something. • I caught the pocket of my trousers on the drawer pull and almost ripped it off. • He caught the sleeve of his uniform on a branch., Phrase(s): catch on (to something)
Fig. to figure something out. (See also get onto someone.) • I finally caught on to what she was talking about. • It takes a while for me to catch on., Phrase(s): catch on (with someone)
Fig. [for something] to become popular with someone. • I hope our new product catches on with children. • I’m sure it will catch on.
McGrawhill's American Idioms And Phrasal Verbs