English word mandatory comes from Latin mandator (Mandator, commander, director.)

Detailed word origin of mandatory

Dictionary entry	Language	Definition
mandator	Latin (lat)	Mandator, commander, director.
mandatorius	Late Latin (LL)
mandatory	English (eng)	(dated, rare) A person, organisation or state who receives a mandate; a mandatary. Obligatory; required or commanded by authority.. Of, being or relating to a mandate.