The closest parallel to this entry (containing both of the etymologies offered here) is in an anonymous Etymologicum published in Anecdota Graeca (Cramer) 2.436.20.
1An absurd etymology based on the similarity between the words 'intestine' (e)/nteron) and 'different' (e(/teron). The same etymology is also offered in entries on e)/gkata ('innards') in Etymologicum Magnum 310.9 and Etymologicum Gudianum 394.19.↩
2Another etymology, as if e)/nteron were a combination of words for 'within' (e)nto/s) and 'flow' (r(ei=n). Also found in Etymologicum Magnum 344.32. Cf. the similar etymology in Etymologicum Gudianum 480.13, where the word is derived from 'fitting' (a)rhre/nai) within.