[Dave, Melbourne,Australia]

The suggestions from this thread and the 14Aug2008 Vocabulary Terms thread 18784 mentioned above by JJ are:
Adieu (but I have to subtract it due to The Sound Of Music's "So Long, Farewell")
Assinaboine
Casino Rama
Catbird
Chaste
Chibougamau
Couchiching
Dumoine
Finery
Flagon
Flotsam (but subtracted as on a Peter Gabriel album)
Flywheel
Gentry
Gitche-Gumee
Hangdog
Hexagram
Hornepayne
Ironcast
Ironclad
Joneses
Kinsale
Lee (of an island etc)
Mariners
Mendocino (but I have to subtract it due to Kate & Anna McGarrigle's "Talk To Me Of Mendocino")
Muskeg
Muskie (but subtracted due to "Muskie Maniac")
Navvies
Nous Vivons Ensemble (and other French vocabulary in that song)
Oft-times
Penzance (I don't think any songs from "The Pirates of Penzance" mention the actual town)
Polka Dot Underwear
Prima Donna (but I'm sure it's heard in a song on Van Morrison's album "A Night in San Francisco")
Quietude
Resolute
Ringneck
Rural Sprout
Scrimshaw (which apparently isn't in American dictionaries but as an irrelevant segue I remember an Ian Scrimshaw playing for Hawthorn in the Australian Football League)
Spectre
Starcase
Stemming
Tattletale (but subtracted due to Faron Young's "Tattle Tale Tears")
Uptight
Verdant
Vocabulary
Wherefore.

I can't recall some of those words in Lightfoot songs, but I have no reason to doubt the people suggesting them. I probably shouldn't have suggested a place name like Kinsale, as Gord has sung a lot of place names and many would have appeared in songs recorded by famous and/or unknown artists. There would also be a good argument for leaving multiple-word expressions and non-English-language words off the list.