OAH.com. ...

All three letter .com domains have been registered for years.  OAH.com is no exception.  This name was originally registered 18 years ago, back in 1996.
OAH.com has value because there are a finite number of three letter .com domain names in existence.  Additionally, a small percentage of those names are comprised of three highly-desirable letters.  OAH.com is perfect for an investment in digital real estate, or it would be a great asset to use for your online identity. 
Three letter .com domains have steadily appreciated in value because they are limited in supply, yet very much in demand from investors and end users.