cotton on
US /ˈkɑːt.ən ɑːn/
UK /ˈkɑːt.ən ɑːn/

1.
begrijpen, snappen
to understand something after a period of not understanding it
:
•
It took him a while to cotton on to what I was saying.
Het duurde even voordat hij begreep wat ik zei.
•
She finally cottoned on to the joke.
Ze begreep de grap eindelijk.