tmesis is the term all right, it is distinguished by being the only word in the OED to begin tm. I know this because it was ont' box t'other night as a question on QI ( and because I checked, never trust a man over 6'4).
tmesis n (pl. tmeses) the separation of parts of a compound word by an intervening word ( used informally for emphasis e.g. I can't find it any-blooming-where)
Origin C16: from Greek tmesis 'cutting'.