Sometimes spelled
snottie, it is a
derogatory term referring to
midshipmen in the
Royal Navy and its
descendents.
Because they tended to be young and it was their first time away from home, they tended to shed a lot of tears. This inevitably resulted in a runny nose, giving them the name snotty.
In an attempt to discourage the midshipmen from wiping their noses on the sleeves of their jackets, the symbol of their rank was three brass buttons on each cuff.