borrowed name; assumed name; alias
Refers to a name that is not one's own, used temporarily or under false pretenses. Often implies deception or concealment of identity.
彼は借り名を使ってホテルに泊まった。
He stayed at the hotel under an assumed name.
その手紙は借り名で送られてきた。
The letter was sent under a borrowed name.
Compound of 借り (kari, 'borrowing') and 名 (na, 'name'). The exact historical derivation is uncertain, but the meaning is transparent from its components.