Where does “molestare” come from?

molestare (Latin) comes from Latin molestus, from Latin mōlēs — multitude, mass (of material).

Ancestry of “molestare”, step by step

Step	Language	Word	Meaning
1	Latin	molestus	troublesome, irksome, grievous, annoying,...
2	Latin	mōlēs	multitude, mass (of material)