cotton on

US /ˈkɑːt.ən ɑːn/
UK /ˈkɑːt.ən ɑːn/
"cotton on" picture
1.

entender, perceber

to understand something after a period of not understanding it

:
It took him a while to cotton on to what I was saying.
Demorou um pouco para ele entender o que eu estava dizendo.
She finally cottoned on to the joke.
Ela finalmente entendeu a piada.