IPA: /əˈkʌstəmdnəs/
KK: /əˈkʌstəmdnəs/
The state of being used to something or being familiar with it, often through repeated exposure or experience.
His accustomedness to the cold weather made it easier for him to enjoy winter sports.
Accustomedness is formed from "accustomed" (from the Old French *acostumer*, meaning to make familiar or habitual) and the suffix "-ness" (meaning the state or quality of). The word refers to the state of being familiar or habitual with something.
Think of becoming familiar with something over time, which is what 'accustomedness' means — it's the state of being used to something.