And-just for the record, there is an African male name "Ottah".

"Othar" and "Otha" could be variant forms of the West African male name "Ottah" {0-TAH}". "Ottah" means "the thin one". This name is reported to come from the Urhobo speaking people of Nigeria. It is given to a male child who is born thin at birth. Source: Ogonna Chuks-orji: Names from Africa: Their Origin, Meaning, and Pronunciation {Johnson Publishing Company; 1972} and Sue Browder: The New Age Baby Name Book {Workman Publishing, 1987}.

Btw, I've never met anyone by the name Otha, but in the early 1990s there was an African American male student whose name was "Otha" who attended the same university as my daughter.

If I were a betting person {which I'm not}, I'd bet that the Nigerian male name "Ottah" is the source of the African American male name "Otha". The change in spelling & pronunciation between these two names might be the result of time & cultural/ethnic sound preferences.

Note that I'm not saying that the African name Ottah was the source of Othello's name. I'm sharing this information just because some might find it interesting.

Also, I want to thank fellow Mudcatter Tweed for hipping me to African American fife musician Othar {Otha} Turner.

See http://www.shs.starkville.k12.ms.us/mswm/MSWritersAndMusicians/musicians/OtharTurner/Turner.html
for information about this Mississippi musician.