shirttail

Short definition from Wiktionary

Noun

1. 1
   The single or split (then rather plural) bottom part of a shirt, below the waist, especially in the back, which, when not tucked into trousers or other vestment, hangs over the wearer's tail-end, like a tail.
2. 2
   The tail-end or periphery of something.
3. 3
   A tenuous connection.
4. 4
   A distant kinship.
5. 5
   A small portion
6. 6
   Something small and unimportant.