Boukólos rule


The boukólos rule is a phonological rule of the Proto-Indo-European language. It states that a labiovelar stop dissimilates to an ordinary velar stop next to the vowel or its corresponding glide. The rule is named after an example, the Ancient Greek word βουκόλος "cowherd", ultimately from PIE. The second constituent of this word was originally, which can be seen from the analogously constructed αἰπόλος "goatherd" <. The same dissimilated form is the ancestor of Proto-Celtic, the source of Welsh bugail.
Another example could be the Greek negation οὐκ, which Warren Cowgill has interpreted as coming from pre-Greek *ojukid <, meaning approximately "not on your life". Without the boukólos rule, the result would have been *οὐτ.
The rule is also found in Germanic, mainly in verbs, where labiovelars are delabialised by the epenthetic -u- inserted before syllabic resonants: