1670s, from Norwegian fiord, from Old Norse fjörðr "an inlet, estuary," from North Germanic *ferthuz "place for crossing over, ford," from PIE *pertu-, from root *per- (2) "to lead, pass over." The etymological sense probably is "a going, a passage."
"arm of the sea, estuary of a river," early 15c., Scottish, from Old Norse fjörðr (see fjord).
"stream, creek," 1630s, American English, from Dutch kil "a channel," from Middle Dutch kille "riverbed, inlet." The word is preserved in place names in the Mid-Atlantic American states (such as Schuylkill, Catskill, Fresh Kills, etc.). A common Germanic word, the Old Norse form, kill, meant "bay, gulf" and gave its name to Kiel Fjord on the Baltic coast and thence to Kiel, the German port city founded there in 1240.