Latin word inflammo comes from Latin ingratus (Thankless. Ungrateful. Unpleasant, disagreeable.), Latin flammare

Detailed word origin of inflammo

Dictionary entry	Language	Definition
ingratus	Latin (lat)	Thankless. Ungrateful. Unpleasant, disagreeable.
flammare	Latin (lat)
inflammo	Latin (lat)	I excite.. I ignite, inflame.