Tied at both ends

Does anybody know the phrase "tied at both ends"? In the text where I found it, it does not seem to have the literal meaning. Btw, it's a J-Tull song, and they seem to like using loads of regional expressions.

Here's an excerpt of the song from willerup.com/ tull/lyrics/passion.html :
Old gentlemen talk of when they were young
Of ladies lost and erring sons.
Lace-covered dandies revel with friends
Pure as the truth tied at both ends.

I have to say most of it makes very little sense to me.

I think ingesting quantities of illegal substances is a first step in writing - or understanding - such logorrhea. Of course, poetry doesn't have to "make sense" any more than tonight's dinner has to "make sense." Poetic license. It seems like rubbish to me, but might be high art to someone else.

That having been said, "tied at both ends" seems more understandable than 90% of that lyric. The truth can presented, as we sometimes say, tied up with a pink ribbon. Packaged and complete. No messy ambiguities leaking out the back. Nothing unresolved. Think of a sausage casing, tied at both ends, complete and finished.

--could it be along the same lines as "buttoned up the back" and similar phrases.

Meaning stupid.

"Do you think I am tied at both ends?"