This is a guy's name. It is extremely rare. The original Arabic word is Hasanain, which means two Hassans. Most Arabic words can be transformed from singular to dual by adding an "ain" sound at the end.
The name is a combination of the two grandsons of Prophet Muhammad, Hassan and Hussein.
Hassan literally means "good".
Hussain means Younger Hassan.
Stranger: Hey nice to meet you, whats your name?
Stranger: Sorry, come again---Ha?
Me: Just call me Haz.