originator; proposer; initiator
Refers to the person who first came up with a plan, idea, or proposal. Often used in formal or business contexts.
He is the originator of this project.
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.