I was also intrigued by the language the villagers spoke. At first I thought I heard German words, then it sounded more like a Scandinavian language. Sometimes the names of the characters give away information, so I looked through the credits and found a "Jonhard Mikkelsen" listed as "translator", I googled the name and found an author by ...
I honestly think most sources misinterpret this a bit. A more natural flow would be:
Holliday: "In vino veritas" / in drunkenness, truth
Ringo: "Age..." / Do what you do best
Holliday: "Credat..." / (allusive) Believe what you want to believe
Ringo: "Juventus..." / Youth teaches fools
Holliday: "In pace..." / ...
This is what he had said earlier,
... Remember back in college, when he fell in love with Carol and bought her that ridiculously expensive crystal duck?
Later when Rachel questioned him,Chandler said:
[stuttering incoherently] F-hah.... flennin....
He actually jumbled up the letters of fell in love and created a meaningless word "flennin".
It is a parody of a type of bad writing sometimes known as said-bookism, where authors keep a book of alternative words to use instead of said. Examples:
"Yes" he muttered.
"Yes" he whispered.
"Yes" he roared.
"Yes" he exclaimed.
"Yes" he hissed.
"Y-Y-Yes" he stuttered.
A variation is to use ...