Seemingly not much of a specialised railway enthusiasts' meaning, then. (I recall, a few decades now, a young enthusiast whom I briefly met, talking -- rail context -- about a "gen trip"; which baffled me a bit.)
My bolding: I gather that "puggie" or just "pug", is additionally, a highly venerable Scottish term in railway contexts -- generally used in olden days, to denote a small steam tank loco. I was once acquainted for a short time with a Scots lad -- not the "gen trip" guy mentioned above -- who was a keen steam preservationist, and a slightly strange individual: now and again he would (a propos of nothing in particular) joyfully screech, fortissimo, "PUGGIES !".
I read, long ago now, a memoir by an elderly enthusiast who had served on the Western Front in the final year of World War I. He wrote of himself and comrades being conveyed by train on one occasion, from one place to another of the front. It was a long, heavy train: was banked for a spell, by an enormous Du Bousquet type articulated double-six-coupled tank loco, which would seem to have been brought in as an emergency measure, from elsewhere in France. Some members of a Scottish regiment were in the same vehicle as the memoirist and his squad: he recounted the Scots' officer referring to the banker as a "Frog pug", which description struck him as quite magnificently inappropriate.