The Spanish verb 'hornear' (to bake) comes from combining the noun 'horno' (oven) with the verbal suffix '-ear'. The noun 'horno' itself derives from the Latin word 'furnus', meaning 'oven'. The initial Latin 'f-' sound evolved into 'h-' in Spanish, a common sound change in the development from Latin to Spanish. The suffix '-ear' is commonly added to nouns in Spanish to create verbs meaning 'to do something with/using (the noun)'. So 'hornear' literally means 'to do something using an oven' - in other words, to bake.

The most obvious related Spanish word is 'horno' (oven), which is simpler and more commonly encountered than the verb 'hornear'. You might see 'horno' on kitchen appliances or in recipes. Another related word is 'hornada' meaning 'batch of baked goods' or 'fornido' (sturdy, robust) which surprisingly comes from the same Latin root, with the idea of something being 'oven-hardened'.

While not immediately obvious, English 'furnace' is a cousin of Spanish 'hornear', as both trace back to Latin 'furnus'. The English word maintained the original 'f-' sound while Spanish changed it to 'h-'. A furnace, like an oven, is essentially an enclosed heating chamber. The word 'furnish' also comes from this same Latin root, originally referring to the provision of heat or warmth, though its meaning has broadened considerably over time.