A Slavic name most common in Russia (e.g. the opera "Ruslan and Ludmila"), but also in Bulgaria, Ukraine, etc.
The name originally comes from Rostam, a national hero in Iranian mythology. It was later borrowed by Turkic peoples as Arslan or Aslan, and subsequently by Russian people as Yeruslan, from which the modern name comes.
The meaning of this name is "lion", and a small number of sources give an etymology of "big".
Person: Hey, what's your name?
Ruslan: I'm Ruslan, nice to meet you.
Person: Ooh, govorite po russkiy?
Ruslan: Nah, sorry, I'm from Bulgaria.