Paddy describes the working conditions on the railway: "In (1841), I put me corderoy britches on... to work upon the (railway)." He recalls the hard work, courting and losing a wife, and the drink he uses to relieve his burdens
Greenway prints a three-verse version ending with complaints about the company store. It is not clear whether this is a parody or a natural addition -- or whether the Sandburg/Lomax versions have cleaned this up.
There is a broadside, NLScotland LC.Fol.178.A.2(086), entitled "Paddy on the Railway," beginning "A Paddy once in Greenock town, For Glasgow city he was bound." The chorus is "Engine, boiler, water tight, Driving in with all his might, Upon my soul it was a sight To see the Greenock railway." This may well be related; I wouldn't consider it the same song. Cohen thinks there is "no relation."
Cohen also discusses the origin of this song, observing that it has two basic forms, which might be distinguished by their choruses -- the one more common in old versions being "I'm weary of the railway, Poor Paddy works on the railway"; the other, which is the one they taught us in grade school, is "Fil-i-me-oo-ri-ee-ri-ay" or some such noise. Cohen hints darkly about the fact that the earliest source of the second tune is a Lomax book, and I can offer no contrary evidence. There is also evidence of mixng of versions; Cohen notes the similarity of these several Lomax verses to the undated broadside "Mick Upon the Railroad."
Shay describes his version as a capstan chantey. The only support for this is the last of his nine verses, in which the singer goes to work for the Black Ball Line in 1849 ("and that's the end of my monkeyshine"). It is clear that the song functioned as a shanty of some sort, though, given the number of sea song collections in which it is found.