Where are you getting this derivation? Any Hebrew cognate of this word is interesting, but you can't use that cognate as evidence to supersede the meaning it actually has in Aramaic.
To wit, if you go to Jimmy Akin's site, you'll see this very issue of "hollow rock" is discussed.
Forget about the apologetic stuff there for the moment, and just skip down to the center of the thread, where you'll see a scan Jimmy has from "A Compendious Syriac Dictionary" by R. Payne Smith. Syriac is of course a dialect of Aramaic.
Take a look at the definitions there that are given for Kepha: stone, rock, stone vessel, column, idol, grindstone, whetstone, millstone, etc. Nothing there about hollowness. You could probably make a case for a vessel being a hollow stone. But there are plenty more meanings where you can't....whoever heard of a hollow grindstone or millstone?
I read your link but none of those definitions of “keepa” are anything upon which a church could be built. They are however in line with the Hebrew “keph”, which may not be the “hollow rock” that Strong’s describes, but is also not the substantive rock described by the Hebrew “tsur”, the rock foundation for the city of Tyre, and “cela, selah” which incidentally became the rock city we know today as “Petra” — not “Petros” or “Cephas”.