Бывают ли усы до плеч : семантика праславянского *bъrkъ и её дрейф в языкахпотомках

The article is an attempt to establish the original semantics of Proto-Slavic *bъrkъ and describe semantic drifts of its continuants in the modern Slavic languages. Oleg Trubachyov’s hypothesis that ‘shoulder’ > ‘hair down to someone’s shoulders’ > ‘beard and moustache down to someone’s shoulders’ was the main semantic shift, which its turn could prove his etymology of the word *ǫsъ, is questioned and put to the test. The author comes to the conclusion that the most probable protomeaning of the word was ‘hollow shaft of a feather’, which had further developed into ‘moustache’, ‘flight feather’, ‘forearm/shoulder’ and others. The findings of the research make the author believe that Trubachyov’s hypothesis cannot be considered reliable.