Pardon me if this is an uncouth phrase but I heard it and tried to find out what it meant but to no avail. What does navvy sp. (sounded like nah-vey) mean?

If you mean what I think you mean its like a labourer or a workman

Great, thats what I mean, thanks!

It comes from 'navigator'. That's what the people who built the canal system (the 'navigation') in Britain in the 18th and 19th centuries were called.