Groggy Linguistics

I'm sick. I shouldn't be online. But just wanted to prattle on about a thing that'd take too long on twitter. A day or two ago I came across a linguist being cited somewhere in some article about celebrity couple name blends. In it they noted how certain syllables like "klol" and "prar" are forbidden in English. They phrased the restriction as forbidding CRVR (where C means a consonant, R means a liquid/sonorant —I forget how they phrased it—, and V a vowel).

There's something of merit going on here, but the specifics are far more complicated. Note that "slur" is perfectly acceptable. So, well maybe it's just that the C has to be a plosive. But then, "blur" is perfectly fine too. So, well maybe it's something special about how "-ur" forms a stand-alone rhotic vowel. But then "trill" and "drill" are just fine. So, well maybe...