1
general::
Phrase(s): thereby hangs a tale
there is an interesting story connected with this matter. • Yes, she comes in late most mornings, and thereby hangs a tale. She has a drinking problem.
McGrawhill's American Idioms And Phrasal Verbs
2
general::
That detail or incident reminds one of another story, as in So he went without supper, but thereby hangs a tale. This expression, embodying the pun on tail and tale, was used by Shakespeare in at least four of his plays and presumably was well known before that. [1500s]
American Heritage Idioms