firth/fɜːθ/Etymology* As an English and Scottish surname, from Old English fyrhþe (“forest”). * As a Scottish surname, from Firth in Orkney, itself from Old Norse fjǫrðr (“firth”). * As a Welsh surname, from ffrith, itself borrowed from the first sense.firth means A surname. Lexicurio rates it Rare gem — a strength score of 80 out of 100.nameA surname.A town in Bingham County, Idaho, United States.A village in Lancaster County, Nebraska, United States.A parish on the Bay of Firth, Mainland, Orkney Islands council area, Scotland (OS grid ref HY3514 (approx.)A small village in north-east Mainland, Shetland Islands council area, Scotland (OS grid ref HU4473).A hamlet south-east of Lilliesleaf, Scottish Borders council area, Scotland (OS grid ref NT5423).nounAn arm or inlet of the sea; a river estuary.“The descent continues, still more steeply to Dundee (Tay Bridge), and approaching from the bridge itself this sharp descent gives the curious appearance that the station is below the level of the firth.”