The Spanish verb 'pedir' (meaning 'to ask for' or 'to request') comes from the Vulgar Latin '*pedere', which meant 'to request'. This Vulgar Latin form developed from the Classical Latin word 'petere', which had the meaning 'to seek' or 'to request'. The evolution from 'petere' to 'pedir' shows a common sound change where the Latin 't' became 'd' in Spanish, and the final '-ere' verb ending evolved into '-ir', which is now one of the standard verb endings in Spanish.

Some common Spanish words related to 'pedir' include 'pido' (I ask for), 'pedido' (order/request), and 'despedir' (to say goodbye, literally to 'un-request' or 'send away'). The noun 'petición' (petition) is also related, maintaining the 't' from the original Latin form.

Several English words share the same Latin root 'petere'. These include 'petition' (a formal request), 'compete' (originally meaning 'to seek together'), 'appetite' (a seeking after food), and 'perpetual' (continuing to seek through time). The 'pet-' root in these English words maintains the original 't' sound from Latin, while Spanish evolved to use 'd' instead.