part of the furniture
US /pɑːrt əv ðə ˈfɜːrnɪtʃər/
UK /pɑːrt əv ðə ˈfɜːrnɪtʃər/

1.
家具の一部, おなじみの存在
a person or thing that has been in a place or situation for so long that they are considered a permanent, unremarkable, or indispensable feature of it
:
•
After working here for twenty years, John has become part of the furniture.
ここで20年間働いた後、ジョンは家具の一部になった。
•
The old clock in the corner has been there so long it's just part of the furniture.
隅にある古い時計は、あまりにも長い間そこにあったので、もはや家具の一部だ。