same temperament; kindred spirit
Literary or somewhat old-fashioned term for people who share a similar disposition or way of thinking. Not common in everyday speech; more often expressed as 気が合う or 似た者同士.
Since we are of the same temperament, we hit it off right away.
Compound of 同 (same) and 気 (spirit, temperament). The exact historical derivation is uncertain, but it follows a classical Chinese pattern for describing shared inner qualities.