means A book, app, or person used to organize tasks, appointments, and goals across time so you can plan ahead.

from From "plan" plus the agent suffix "-er." "Plan" entered English in the 17th century from French plan, meaning a flat surface, drawing, or ground layout — itself rooted in Latin planus, "flat, level." The word first described the literal layout of a building (a floor plan) before it stretched into the figurative sense of a scheme or design for the future. A "planner" is simply one who — or that which — makes such plans.