Transpogram
A word or phrase becomes another when divided into two parts, which are interchanged. Examples: alloy, loyal; or tactic, Tic Tac; or ingrain, raining; or onslaught, Laughtons. Answers must have dictionary nature (or be well known) but, as in these examples the parts need not.
A transpogram is most interesting if the parts have substantially different meanings. Houseguest and guest house, for example, are a dull base. Since interesting bases are hard to come by, the transpogram has always been an uncommon type.
In a reversed transpogram, the result is reversed after the two parts are interchanged. Examples: parrot, raptor; or mutual, umlaut.
In a phonetic transpogram, the two parts that switch remain true to sound but not to spelling. Examples: zero, rosy; or pinky, keeping; or except, septic.