The Spanish word 'dicho' (meaning 'saying' or 'expression') comes from the Latin past participle 'dictus' meaning 'said', which itself derives from the Latin verb 'dicere' meaning 'to say'. The evolution from Latin 'dictus' to Spanish 'dicho' shows a typical sound change where the Latin 'ct' cluster evolved into 'ch' in Spanish, a pattern seen in many Spanish words of Latin origin.

A very common related Spanish word is the verb 'decir' (meaning 'to say'), which comes directly from the same Latin root 'dicere'. While 'decir' is the action of saying something, 'dicho' evolved to refer to the thing that is said - particularly a common saying or expression. You might recognize 'dicho' in common Spanish phrases like 'dicho y hecho' (said and done) or 'como ya he dicho' (as I have already said).

Several English words share the same Latin ancestor 'dicere'. Some common examples include 'dictate', 'dictionary', 'dictum', 'predict', and 'verdict'. Each of these words relates to speaking or saying: a 'dictionary' contains words that have been 'said' or defined, to 'dictate' is to say something for others to write down, and a 'verdict' (from Latin 'vere dictum' meaning 'truly said') is what a jury or judge says at the end of a trial.