1
general::
Put on clothes for a particular activity, as in Come on, fellows, it's time to suit up for the hockey game. [Mid-1900s]
American Heritage Idioms
2
general::
Phrase(s): suit (oneself) up
to get into one’s uniform, especially an athletic uniform. • The coach told the team to suit up for the game by three o’clock. • It’s time to suit up! • She suited herself up and went out on the court.
McGrawhill's American Idioms And Phrasal Verbs