"Two Shits" as in "I don't give..."
Heard by Det Commanders, Section Commanders, grizzled ex-ranker Officers and the odd Platoon Commander who has had enough of the TA chappy attached to his ARAB goons (mainly because said TA chappy seems to know more about the FFR Rover than he does).
Derived from the "I don't give a f***" heard by US Forces throughout the world, with a "quaint" British angle on it. Some argument over which way the derivation goes.
May yet be a nickname for John Prescott given he's already been Two Jags, Two Jabs and Two Shags.
Also a description for a bloke who always has to go one better. If you've had a shit, he's had two shits. See Elevenariffe.