The Spanish word 'árbol' (meaning 'tree') comes from the Latin word 'arbor', which also meant 'tree'. The word evolved through Old Spanish 'áruor' before reaching its modern Spanish form. During this evolution, the Latin 'b' in 'arbor' first became a 'u' sound in Old Spanish (a common sound change), and then later changed to 'l' in modern Spanish, giving us 'árbol'.

While 'árbol' itself is a basic and common Spanish word, it has given rise to several related Spanish words like 'arboleda' (grove of trees), 'arbolado' (wooded area), and the diminutive 'arbolito' (little tree). These words are all built from 'árbol' as their root word.

The Latin root 'arbor' has given English several related words, including 'arboreal' (relating to trees), 'arboretum' (a botanical garden focused on trees), and 'arbor' (a garden structure often covered with climbing plants). While these English words might be less common in everyday speech, understanding their connection to the Spanish 'árbol' can help remember that they all relate to trees.