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Vulgar Latin *convĭāre
Vulgar Latin had another verb derived from vĭāre, namely *convĭāre, which meant ‘to go together on the road, to accompany on the way’ and, derived from that meaning, ‘to escort’. This verb was derived by means of the prefix com- ‘together’. This verb did not get passed on to Spanish, but it resulted in convoier in Old Central French and in conveier in Old Northern French, and both versions of the verb got passed on to English, both in the 14th century.
Old French convoier, meaning primarily ‘to escort’, became Eng. to convoy [ˈkɒn.vɔɪ̯], originally pronounced with final stress. This verb today means ‘to travel with something in order to protect it’ (DOCE). This verb came first into Scots English with the senses ‘to convey’, ‘to conduct’, and ‘to act as escort’. The main Spanish equivalent of this verb is escoltar, a cognate of Eng. escort. The loanword convoyar has also been used for this meaning in Spanish, but it is very rare.
The noun convoy, also pronounced [ˈkɒn.vɔɪ̯] in Modern English, like the verb, means ‘a group of vehicles or ships travelling together, sometimes in order to protect one another’ (DOCE). The noun convoy does not appear in English until the 16th century, two centuries later than the verb. It may be a back-formation from the English verb to convoy or else, it may be a borrowing from French convoi [kɔ̃.ˈvwa], a noun derived from the verb convoier which, speaking of vehicles or ships, meant ‘to convoy’, though it has can also be used with the sense of 'procession', as in convoi funèbre ‘funeral procession’. At least originally, Fr. convoi conveyed the sense that some of the members of the convoy were escorting others, typically for protection.
Spanish borrowed the noun convoy, pronounced [kom.ˈboi̯], in the 17th century, with the same meaning it has in English and spelling pronunciation (plural: comboyes). Presumably, it was borrowed from French convoi, though the Spanish word’s spelling is like that of the English word, with a final y, but that is most likely due to the fact that that is how the diphthong [oi̯] is spelled at the end of a word in Spanish.
Another possible Spanish translation for Eng. convoy is caravana. The expression to travel in convoy translates into Spanish as viajar en convoy or as viajar en caravana. Eng. caravan originally meant ‘a group of people travelling together across a desert in Asia or North Africa’ (COED). Nowadays, the main meaning of this word in North America is ‘a covered motor vehicle with living accommodation’ (Sp. caravana, casa rodante, etc.) and in Britain, ‘a vehicle equipped for living in, usually designed to be towed’ (COED) (Sp. caravana, rulot, remolque). (A gypsy caravan or covered cart is known as carromato in Spanish.) The ‘procession’ sense of Eng. caravan can also be translated as caravana or, more commonly, as procesión. (The noun procession can be defined as 'a number of people or vehicles moving forward in an orderly fashion, especially as part of a ceremony' and, derived from this meaning, 'the action of moving in such a way' and 'a relentless succession of people or things', COED.)
The cognates Eng. caravan ~ Sp. caravana, were probably borrowed from French caravane. The Spanish word is first documented in the 14th century and the English one, in the 16th. The ancestor of this word is first attested in Europe in Medieval Latin in the 12th century, with different spellings having been recorded: carvana, caravanna, caravenna. It is a word picked up by Europeans in the Middle East during the Crusades and it comes ultimately from Persian کاروان (kârvân) ‘caravan, convoy’, a word derived from the Proto-Indo-European root *ker‑ ‘army’. (English had a now obsolete word here that meant ‘army, hostile force’ that descends from the same PIE root.)
The other Old French reflex of Vulgar Latin *convĭāre is conveier, which was borrowed into English as the verb to convey [kən.ˈveɪ̯], also in the 14th century. The modern meanings of this word are ‘transport or carry to a place’, ‘communicate (an idea, impression, or feeling)’ and, in legal terminology, ‘transfer the title to (property)’ (COED). The verb convey has different translations into Spanish, the most common of which are transportar (goods and people) and transmitir, comunicar, expresar (ideas, feelings, thanks, sound, electricity). In legal terminology, to convey translates as traspasar (a cognate of Eng. trespass) or transferir (a cognate of Eng. transfer).
 Note that this verb does not seem to have been used in Classical Latin. Latin did have verb convehĕre ‘to carry, bear, or bring together’ (L&S), which is not related to the Vulgar Latin verb, despite going back to the same Proto-Indo-European root and contain the same prefix. There are no reflexes of this Latin verb in neither Spanish or English.