A chain that is very badly knotted and cannot be unraveled is inextricable. You cannot disentangle it.
Inextricable comes from the Latin prefix in- meaning "not" and extricare meaning "unravel." Something that is inextricable cannot be unraveled. This isn't just limited to objects. Memories from childhood can sometimes be inextricable from other associations — so bound up that it is hard to separate one from the other.