They are called this because they are usaualy phoned just before or during a fight so they arive late and catch the rival gangs by surprize
can also be :
ringing in "that dude is always ringing in"
rings in " fred always just rings in "
kinda like gate crashing but not in more of an everyday life sence
Someone, not a regular member of a team, who has been surreptitiously brought in for one match because they have superior skills to the person who normally plays in that position.
In horse racing, A fast horse disguised as, and racing under the name of a known slow horse. So those involved can bet at high odds and get a large winning payout from the bookmakers
One of the biggest scandals in Australian horse racing was the Fine Cotton ring in