[Word Family: adjective: ↑customary, ↑custom, ↑customizable, ↑accustomed; noun: ↑custom, ↑customer, customs; verb: ↑accustom, ↑customize; adverb: ↑customarily]
[Date: 1400-1500; Language: Old French; Origin: acostumer, from costume 'custom']
to make yourself or another person become used to a situation or place
accustom yourself to something
It took a while for me to accustom myself to all the new rules and regulations.