Pronto: This has various meanings in the Romance Languages however the meanings are slightly similar in some cases.
In Italian for example it means ready. As with the English language it is normally used in conjunction with the verb essere meaning to be. It can mean prompt or fast in certain circumstances for eg; pronta consegna meaning fast delivery. However it is also widely used when answering a phone call even though it does not actually mean hello.
In Spanish pronto means early or fast or soon.
In French it does not exist however the word prêt means ready like for example in prêt-à-manger meaning a ready made meal. In French when a word has a circumflex ^ also known as a hat, it usually substitutes the s that previously existed in the original Latin word thus changing it to prest, in Latin. However in Italian the word presto exists meaning soon, fast and early used in exactly the same way as Pronto is in Spanish.
This leads us (or at least me) to think that these 2 words Pronto and Presto whose meanings sometimes overlap must have been confused during the development of these modern languages.
I don't speak any other Romance languages so if you know of any more where Pronto has one of the above meanings please add them on or tell me and i'll add them to this. Thanx