Renward Brandstetter, An Introduction to Indonesian Linguistics…
“ Some of the phenomena that are usually regarded as variations could perhaps with equal justification be classed under the concept of determination. It is customary to say that suk in Old Jav. asuk, “to bring into”, and sup in susup, “to force one's way into”, stand in the relation of variation to one another. But it is also a tenable view that suk and sup are cases of the determination of a root of two sounds, su. But this would remain a mere figment of the imagination until it had been shown that such a root su had a real existence. ”
