I cannot put my admiration of this man into mere human words.
(This video is from the BBC Archive)
The languages were the first thing Tolkien created for his mythos, starting with what he originally called "Qenya", the first primitive form of Elvish. This was later called Quenya (High-elven) and is one of the two most complete of Tolkien's languages (the other being Sindarin, or Grey-elven). The phonology and grammar of Quenya are strongly influenced by Finnish, Latin, Greek and elements of ancient Germanic languages, and Sindarin is strongly influenced by Welsh.