noun
attorney-in-fact
A person authorized to act on another's behalf through a written power of attorney. Used in legal and business contexts.
委任状による代理人が契約書に署名した。
The attorney-in-fact signed the contract.
彼は委任状による代理人として不動産取引を進めた。
He proceeded with the real estate transaction as an attorney-in-fact.
Compound of 委任状 (power of attorney) + による (by means of) + 代理人 (agent). The phrase is a direct legal term without a deeper historical derivation.