This is a detail of the fresco called "The birth of Jesus" (dated to 1346) from the Serbian monastery Pećka patrijaršija lokated in Kosovo. The old shepherd in the fresco also wears fleece trousers.
The strange sheep on the fresco are "Racka" (meaning Serbian) sheep. I wrote about this strange sheep in my post "Racka sheep".
Now meet Pan, Ancient Greek god of the wild, shepherds, flocks, nature of mountain wilds... Is it possible that the "goat legs" of Pan were not originally not goat legs at all, but highland shepherd fleece trousers, misinterpreted by coastal Greeks to be goat legs?
After all in Greece the worship of Pan began in Arcadia which was always the principal seat of his worship. Arcadia was a district of mountain people, culturally separated from other Greeks.
Shepherd deity, the protector of flocks would be imagined by shepherds like a shepherd, dressed the way shepherds dress, which includes the fleece trousers.
If you didn't know what you were looking at, you could be forgiven for thinking that you were looking at a man with goat legs when you saw one of these highland shepherds for the first time in a distance...And this is how myths are made...