"
eggs
And the Main trunk carried off both me
Scaryblonde may be right, but a falling truck isn't highly damaging. I suspect the original may have been Main Top, a massive structure half-way up the main mast which supports the top mast. And carries a fighting position, where the author may have been at the time. When the mast came down, the top is several tons of falling mayhem; the truck is only a few pounds or tens of pounds. Then again, to a non-nautical singer, perhaps "main trunk" as in the mast itself, may have sounded OK. There is no such thing in nautical jargon however.