The Spanish verb 'prometer' (to promise) comes from the Latin word 'promittere', which was formed by combining two Latin elements: the prefix 'pro-' meaning 'forward' or 'in front of', and 'mittere' meaning 'to send'. When these elements came together, 'promittere' literally meant 'to send forth', but it developed the meaning 'to promise' because making a promise is like sending your word forward or putting it forth. This meaning carried through as the word evolved from Latin into Spanish.

Several common Spanish words share the same Latin roots as 'prometer'. Words containing 'mit' from Latin 'mittere' include: 'permitir' (to permit/allow), 'admitir' (to admit), 'transmitir' (to transmit), and 'emitir' (to emit). All these words carry the basic idea of 'sending' something in different ways. The prefix 'pro-' appears in many Spanish words like 'producir' (to produce) and 'proponer' (to propose), where it maintains its meaning of 'forward' or 'forth'.

English speakers can easily connect 'prometer' to the English word 'promise', which comes from the same Latin root 'promittere'. Other related English words that share the 'mit/miss' root from Latin 'mittere' include 'admit', 'permit', 'transmit', 'emit', 'mission', and 'missile' - all of which involve the concept of sending something. The prefix 'pro-' is also familiar in English words like 'proceed', 'produce', and 'project', where it carries the same meaning of 'forward' or 'forth'.