suitable person; qualified person; right person for the job
Refers to a person who is well-suited for a particular task, position, or responsibility, often implying the necessary skills or qualities.
We are looking for a suitable person for this job.
He is the right person to be the leader.
unqualified person; incompetent person; square peg in a round hole
best qualified person; most suitable person
Compound of 適任 (suitable for a post) + 者 (person). The exact historical derivation is straightforward; the word is a standard Sino-Japanese compound.