The Spanish word 'sordo' meaning 'deaf' comes directly from the Latin word 'surdus', which meant both 'deaf' and 'muffled or dull' when referring to sounds. This is a straightforward inheritance where both the form and meaning have remained remarkably stable over time, with just minor phonetic changes from Latin 'surdus' to Spanish 'sordo'.

The word 'sordo' has given rise to several related Spanish words that Spanish learners might encounter. For example, 'ensordecer' means 'to deafen' and 'sordina' refers to a mute (a device used to dampen or muffle the sound of musical instruments). The adjective 'sordido' (sordid) is also related, though its meaning has evolved to describe something unpleasant or dirty, perhaps from the association of being 'deaf' to moral or social concerns.

English speakers might recognize the connection to words like 'surd' (in mathematics, referring to an irrational number that cannot be expressed as a ratio), which comes from the same Latin root 'surdus'. The English word 'absurd' is also distantly related, as it comes from Latin 'absurdus', which literally meant 'out of tune' or 'deaf to reason', formed from 'ab-' (away from) + 'surdus' (deaf).