Navvy, a clipping of navigator or navigational engineer, mainly refers to the manual labourers working on major civil engineering projects, though it is also used in North America to refer to mechanic
A "navvy" depicted in Ford Madox Brown's painting Work
Wooden huts at the former Edmondthorpe and Wymondham railway station, the last surviving navvy housing in the UK and protected as a Grade II listed building.
Navvies constructing the railway between Stockholm and Uppsala, Sweden (ca 1900).
"McAlpine's Fusiliers" is an Irish ballad, set to a traditional air, which was popularised in the early 1960s by Dominic Behan.
Navvy
…The Pogues song "Navigator" is based on the life of a navvy. Dominic Behan's song "McAlpine's Fusiliers" describes the navvy life. The Genesis song "Driving the Last Spike" describes the life of the navvies…
Alwen Dam in North Wales is only a few miles from where the song's protagonists landed, and was built by Sir Robert McAlpine's company
The song mentions the Isle of Grain. This is the power station there