The Spanish word 'perito' meaning 'expert' comes directly from the Latin word 'peritus', which meant 'experienced' or 'skilled'. This is a straightforward evolution where both the form and meaning remained quite stable from Latin to Spanish, with only minor phonetic adjustments typical of Spanish development from Latin words.

The Spanish word 'pericia' (meaning 'expertise' or 'skill') is a closely related word that comes from the same Latin root. Similarly, the adjective 'peritaje' refers to an expert assessment or expert report. These words form a family of terms in Spanish all relating to expertise and skilled knowledge.

While not immediately obvious, the English word 'expert' is actually a cousin of Spanish 'perito', as it also derives from Latin 'peritus'. The English word came through Old French 'expert', maintaining more of the 't' sound at the end. Another related English word is 'experience', which comes from the Latin 'experientia', related to 'peritus' through the concept of gaining knowledge through practice.