Hello.

Today I learned the phrase "chum up" for the first time. It's not in use today, isn't it? The phrases "hit it off" and "get along" are in pretty common use, aren't they?

chum up
UK OLD-FASHIONED INFORMAL
to become friends:
She chummed up with some girls from Bristol on holiday.


hit it off (with someone)
(informal) to have a good friendly relationship with someone:
We hit it off straight away.


get along
if two or more people get along, they have a friendly relationship:
We've always got along quite well.
get along with
They seem to get along with each other.