The shirt tail cutting may have a military background. In the 30's, newly
commissioned cadets didn't always have the available cash to purchase epaulets
(shoulder boards) some would cut their shirt tails off and use the material to
fashion a set of home made epaulets. Cadets would get their commission and
their wings at the same time and cutting the tails off ones shirt may have
become synonymous with new beginnings, like soloing. This practice led to new
officers being called, "shave-tails" and other things.
JJ Sinclair