planner

The story

1. Proto-Indo-European*pleth₂-?
2. Proto-Indo-European*pel-?
3. Proto-Indo-European*pleh₂-
4. Proto-Indo-European*pléh₂-n̥t-eh₂
5. Proto-Italic*plāntā?
6. Proto-Indo-European*pleh₂k-
7. Proto-Indo-European*pl̥h₂nk /*gteh₂
8. Proto-Italic*plānktā
9. Latinplanta
10. Latinplantāre
11. Frenchplanterdeverb.
12. Frenchplant
13. Frenchplan
14. Englishplan
15. English todayplanner

From plan + -er.