The Spanish word 'sal' (meaning 'salt') comes directly from the Latin word 'sal', which also meant 'salt'. This is one of the most stable words in the Indo-European language family, maintaining both its form and meaning over thousands of years with very little change.

Some common Spanish words derived from 'sal' include 'salado' (salty), 'salero' (salt shaker), and 'ensalada' (salad - which originally referred to salted vegetables). The word 'salario' (salary) is also related, as Roman soldiers were sometimes paid in salt, making it a valuable commodity in ancient times.

The English word 'salt' is a cousin of Spanish 'sal', as both descend from the same ancient root. Other related English words include 'salary' (from the Latin practice of paying in salt), 'salad' (originally referring to salted vegetables), and 'sauce' (which originally meant salted condiments). The word 'saline' (containing salt) is another obvious relative.