Labiovelarize

[...] recently attempted to explain the origin of the Ukrainian form buty, etc., in another way, i.e., through the labiovelarizing influence of the l closing the syllable (resulting from the non- palatalized l).

It is usually defined as a process whereby front vowels consonantalize (palatalize) to the semivowel /j/ when followed by certain other vowels [...] or whereby back vowels consonantalize (labiovelarize) to the semivowel /w/ [...]