One of the reasons that English is described as difficult to learn is the number of words- over 170,000! Of those, the majority are loan-words, words taken from other languages.
The word Rendezvous is one such word. It was appropriated from the French, around 1600 (during a brief period in which Britain and France were not at war- as a result of competition with Spain). The original usage appears to be a verb: rendez vous meaning present yourselves. This then becomes the noun describing the place of meeting we are accustomed to.
English has borrowed from different languages at different times. At the time Rendezvous joined the English vocabulary, a significant number of the new words were coming from French.
About two centuries after Rendezvous was appropriated from the French, William Ashley held the first trappers’ Rendezvous. These lasted for only fifteen years. Some of them were so large as to create temporary towns. Other gatherings in the same time period are occasionally given the same name.. Our local Rendezvous has outlasted the original.