Lyric discussion by WinstonChurch 

Cover art for The Pantaloon lyrics by Twenty One Pilots

From my understanding, "pantaloon" is an Italian term referring to a crazy old guy. This is basically about how his grandfather and immediate father went insane from old age and how he's destined to follow in their footsteps.

"Now it's your turn to be alone, find a wife and build yourself a home." This is referring to how even if you have a wife and home it won't stop you from going insane and feeling alone because you live in your own little world.

It seems as if he made every effort to avoid becoming a "pantaloon" by isolating himself to begin with. The part that talks about his friends fertilizing the ground and how a chair is a tiny island, is a reference to everyone around him starting families while he slowly becomes the "pantaloon."

This is just my interpretation, don't take anything I said for doctrine.

My Interpretation

@WinstonChurch Pantaloon is actually a character in Italy who wears pantaloons (which are like tights for men).