Fiant is an alteration of the German name Fiand which was brought to the US in the mid 18th century as you can see at
http://awt.ancestry.com/cgi-bin/igm.cgi?op=GET&db=ddetling&id=I05575. Fiand is the Low German form of Feind 'enemy, adversary'. You'll find the distribution of Fiant in the US at
http://tr.im/duh6 and of Fiand in Germany at
http://www.verwandt.de/karten/absolut/fiand.html