tmesis

noun

1. the interpolation of one or more words between the parts of a compound word, as be thou ware for beware.

noun

1. interpolation of a word or group of words between the parts of a compound word

1570s, from Greek tmesis “a cutting,” related to temnein “to cut,” tome “a cutting” (see tome). The separation of the elements of a compound word by the interposition of another word or words (e.g. a whole nother).