noun
regular customer; familiar patron
Refers to a customer who visits a shop, restaurant, or similar establishment frequently and is well-known to the staff.
あの居酒屋にはなじみ客が多い。
That izakaya has many regular customers.
彼はその遊女のなじみ客だった。
He was a regular client of that prostitute.
常連 is a more common and general term for a regular customer, without the nuance of familiarity implied by なじみ客.
Compound of なじみ (familiarity, from verb 馴染む) and 客 (customer, guest).