It may depend on the context, but Biejat appears to be Polish, but extremely rare (pronounced: BYEH-yat). In Polish, it comes from an old given name from Latin Beatus, meaning "happy; fortunate; prosperous".
Sources:
https://www.linkedin.com/search/results/people/?keywords=biejathttps://polskienazwiska.pl/n/BIEJAThttps://rcin.org.pl/dlibra/publication/43021/edition/24549/content page 22