The verb accustom means to become used to or familiar with something; to make something a habit. If there is a new baby in your family, you will most likely become accustomed to changing diapers.
Although the verb accustom looks like it should be related to the word custom, it actually comes through costume, through the Old French acostumer, with à, meaning "to," and costume, meaning "fashion or habit." Now it retains the meaning to make something a habit. You can accustom yourself to loud sirens if you live in a city or to the sound of crickets if you live in the country. Parents often cannot become accustomed to the musical taste of their kids.