Irenaeus may have used the same word in his Against Heresies, Book 2, Chapter 13, paragraph 3
(word sometimes translated incomplex
is in bold):
These things may properly be said to hold good in men, since they are compound by nature, and consist of a body and a soul. But those who affirm that Ennœa was sent forth from God, and Nous from Ennœa, and then, in succession, Logos from these, are, in the first place, to be blamed as having improperly used these productions; and, in the next place, as describing the affections, and passions, and mental tendencies of men, while they [thus prove themselves] ignorant of God. By their manner of speaking, they ascribe those things which apply to men to the Father of all, whom they also declare to be unknown to all; and they deny that He himself made the world, to guard against attributing want of power to Him; while, at the same time, they endow Him with human affections and passions. But if they had known the Scriptures, and been taught by the truth, they would have known, beyond doubt, that God is not as men are; and that His thoughts are not like the thoughts of men. For the Father of all is at a vast distance from those affections and passions which operate among men. He is a simple, uncompounded Being, without diverse members, and altogether like, and equal to himself, since He is wholly understanding, and wholly spirit, and wholly thought, and wholly intelligence, and wholly reason, and wholly hearing, and wholly seeing, and wholly light, and the whole source of all that is good—even as the religious and pious are wont to speak concerning God.
I'd imagine "simple" was not used because in the days of Ye Olde English, "simple" was normally opposed to "wise" (as in Psalms where the Scriptures "make wise the simple"). Our language is not simple, but it can be simple sometimes.
If Basil and/or Irenaeus did use asungkerastos
in their respective statements, I believe the meaning would roughly be "not mixed, not compounded". It may have been adopted specifically in refutation to some heretical view(s) regarding God, but that's mostly speculation on my part.