The Spanish verb 'incendiar' (to set fire to) comes from the Latin word 'incendere', which had the same meaning. The Latin 'incendere' was formed by combining two elements: the prefix 'in-' meaning 'in, into' and the verb 'candere' meaning 'to shine, burn'. This combination created the Latin noun 'incendium' meaning 'fire, burning', which evolved into the Spanish noun 'incendio' (fire). The verb 'incendiar' was then formed by adding the Spanish infinitive suffix '-ar' to this noun base.

A simpler and very common related Spanish word is 'incendio' (fire), which is the noun form directly related to 'incendiar'. When you see a news report about an 'incendio forestal' (forest fire), you can connect it to the verb 'incendiar' as the act that might have started that fire.

The English words 'incendiary' (causing or capable of causing fire) and 'incense' (both the noun referring to aromatic material burned in religious ceremonies and the verb meaning 'to make very angry') are related to 'incendiar' through the same Latin root. Additionally, the English word 'candent' (glowing from heat) comes from the Latin 'candere', showing the connection to heat and burning in this word family. The word 'candle' also shares this ancient connection to burning and glowing.