He is said to have created four caskets, which are now called polarities, and hidden them in each of the Four Ages of the World. These caskets ensure that Time City will last throughout a Platonic Year.
"Faber" is Latin, and means "maker of things", "artisan" (or, in some contexts, specifically "smith" - which makes Time City's mythic hero "John Smith").
The form of the name "Faber John" may be related to the mythical king of medieval legend, "Prestor John".
See also A Tale of Time City (spoilers).