*Yusuf is josef, the prophet, and canan is where he is from. for more, check his story in islamic sources (it s pretty close to the bible's story I guess)
*Leyla is a character from an old famous middle east origined love story, leyla and mecnun (or leila and majnoon)
*Yunus is a famous poet who lived in 13rd century (not sure but sth like that) and he wrote his poems in a simple turkish which can be easily understood today. in old poems, poet mentions his name or mahlas(kind of nickname) as a signiture at the last lines, thats why he includes himself in the poem
*sela is some pray words and it is traditionally read when someone dies to let people know. today, you can still see this in small towns. it is also read in special days, like fridays. just consider it like an announcement.