某ぼう氏し

noun

a certain person; Mr. So-and-so; an unnamed individual

Used to refer to someone whose name is withheld or unknown, often in formal or written contexts. Can carry a slightly distancing or discreet tone.

• その件けんについては某ぼう氏しから情じょう報ほうを得えた。

  I obtained information on that matter from a certain person.