The Spanish word 'incendio' (meaning 'fire') comes from the Latin word 'incendium' meaning 'fire' or 'conflagration'. This Latin noun was derived from the verb 'incendere' meaning 'to set fire to', which was formed by combining two Latin elements: the prefix 'in-' meaning 'in, into' and the verb 'candere' meaning 'to shine' or 'burn'.

The evolution from 'candere' to 'incendio' shows how the original concept of shining or burning was modified by the prefix 'in-' to create a more specific meaning related to setting things on fire, which then developed into a noun referring to the fire itself.

A related Spanish word is 'candente' meaning 'red-hot' or 'glowing', which comes from the same Latin root 'candere'. Another related word is 'candela', meaning 'candle' or 'flame', which shares this ancient connection to light and heat.

Several English words share the same Latin ancestor 'candere': 'candid' (originally meaning 'white, pure, bright' before evolving to mean 'honest, straightforward'), 'candle' (from the idea of something that shines), and 'incandescent' (meaning 'glowing with heat'). The 'cand-' root in all these words relates to brightness and heat.