Tmesis. Hard to pronounce, but so much fun, comes from a Greek word, "to cut," and that's what it is. A word is broken in two, and another word inserted, as in "in-freaking-credible." Another, is the strangely emphatic, "West, by God, Virginia." Shakespeare uses tmesis in Romeo and Juliet, "This is not Romeo, he's some other where," but then, Shakespeare has a rather idiosyncratic sense of word order anyway. In the same play, Juliet calls Romeo, "sweet my lord," instead of "my sweet lord," and the apothecary refuses to sell Romeo the poison he wants, worrying that "Mantua's law is death to any he that utters" it. "Any he?" Don't they teach pronoun cases in apothecary college? Tmesis still abounds today, and one piece of tmesis, has become so familiar, that some people have difficulty reconstructing the orginal single word which spawned "a whole nother."