Polish wiki says that
Boris (in Polish
Borys) comes from what's called proto-Bulgarian. First recorded in writing as the name of of
Boris I of Bulgaria:
http://en.wikipedia.org/wiki/Boris_I_of_Bulgaria
Bogus³aw was firt noted in Poland at the beginning of the 13th century.
http://pl.wikipedia.org/wiki/Bogus%C5%82aw
Bronimir is not noted in old Polish writings but it's use is assumed due to several city names that are derived from it.