Once upon a time, when I was a responsible interpretation ranger in Tasmania, I was leading a nature walk with a number of families and a little boy asked me "Why are they called 'bull ants'?"
I squatted down, and as the adults leaned closer so they could hear my pearls of wisdom, looked him in the eye and said: "Because they never tell the truth."

Now I know they are called red bull ants because a sting from one will keep you awake for hours.