originator; proposer; initiator
Refers to the person who first came up with a plan, idea, or proposal. Often used in formal or business contexts.
このプロジェクトの発案者は彼です。
He is the originator of this project.
新しい制度の発案者として知られている。
He is known as the proposer of the new system.
Compound of 発案 (hatsuan, 'originating an idea') + 者 (sha, 'person'). The derivation is transparent from its components.