The Spanish word 'prótesis' (meaning 'prosthesis' or 'addition') comes from the Latin word 'prothesis', which referred to the addition of a sound at the beginning of a word. The Latin term itself was derived from two related Greek words: 'prósthesis' meaning 'addition' or 'attachment', and 'próthesis' meaning 'placing before' or 'exposition'. These Greek roots help explain why 'prótesis' in modern Spanish refers to both artificial body parts (prosthetics) and linguistic additions.

Some related Spanish words include 'prólogo' (prologue) and 'próximo' (next, upcoming), which share the concept of 'placing before' or 'in front of' from the same Greek origins. The prefix 'pro-' in Spanish comes from the same etymological source.

English speakers might recognize this word's connection to 'prosthesis' and 'prosthetic', which come from the same Greek roots. The English word 'thesis' is also related, as it comes from the Greek concept of 'placing' or 'positioning'. Other related English words include 'parenthesis' (placing beside) and 'synthesis' (placing together).