Like a pun, which is a play on terms, "a bit 'C.H.' " is a play on letters... If you were to spell 'bit' as B.I.T. and include C.H. at the conclusion of it, you will get "B.I.T.C.H." It is a sly, notably absurd option to phone some body somewhat bitch. You may also clarify it by-doing that... "you understand, a bit 'c.h.'? ...A little "B.i.t.-- c.h.?"