How does drug get its name? why does it sometimes have two names, e.g. onglyza & saxagliptin?

Trade Name/Clinical: Saxaglipitin is the chemical name which presumably was named by the drug company who created it. Onglyza (saxagliptin) is the brand or trade name saxaglipitin was marketed under. Trade names are chosen for their uniqueness, and drug companies usually undergo extensive public evaluations to determine their acceptance by the public they will be marketed to.