Googled your words, and put them in order that I'd vote.
EBORY - If you gain from the similarity to ebony. If you don't then 5th place for same reason.
OXYGO - Least number of returns, looks like a (r) for a food enzyme or chemical. Maybe known only in Belgium or .za
OXYRA - Looks like a word in Greek or Rumania. Check before choosing.
OBRIA - Most google search results of the 5. Might have conflict or bad connotations. First one was a shoe name by BCBG. Looks like a proper noun in Brazil.
EBORY - 5th if you DON'T gain from the similiarity to EBONY.COM. Looks like a word in Czech, and a surname of some folks.