Both words are derived from the French adjective bouffant/bouffante, "swelling, puffed out". A μπουφάν is a puffy jacket and a scarf puffs out the neck. Both words are unrelated to the English word "buff", which comes from the French buffe, leather (itself from buffle, buffalo). Buff came to mean "to polish/improve leather" -> "improve stats in video game". "In the buff" also thus makes sense as meaning "naked".
It depends on where you are from and what you are used to. There turned out to be many different interpretations for these when we were writing this sentence. We tried to be as neutral and as correct in various regional uses as possible. Check the net images for ζακέτα and you'll see they are knit with buttons. Μποφάν again see the images these look more like ski tops.
SORRY I FORGOT THE LINK: Check out this link for μπουφάν
here < scroll down and look at the images.
I live in Greece and wear a μπουφάν almost daily in winter, as do my children and many other people we know. My husband wears one on weekends. And as mentioned above after many queries and help from Amer., British and Australian users we came up with the names used in this unit.