The Spanish word 'cuello' meaning 'neck' comes directly from the Latin word 'collum', which also meant 'neck'. The evolution from Latin 'collum' to Spanish 'cuello' shows a typical sound change pattern in Spanish where the Latin 'o' diphthongized to 'ue' and the double 'll' simplified to 'll' (which in Spanish represents a distinct sound from a single 'l').

Some related Spanish words include 'collar' (necklace) and 'descolar' (to behead), which both derive from the same Latin root 'collum'.

English speakers might recognize the connection to words like 'collar' and 'collarbone', which also come from Latin 'collum'. The word 'colonel' is also distantly related - it originally meant the leader at the 'column' or neck of a military formation, though its pronunciation has changed significantly over time.