Origin: English, Irish, Persian, Welsh
دالان (Persian) Dalan
Meaning: there wasn't much I could find out about this name. It could be an invented name, a combination of names Dale (meaning "dale, valley") and Lyn (a variant spelling of Lynn from Welsh llyn meaning "lake").
It could also be a variant of Dalan, which seems to be an Irish surname and given name meaning "proud"
It could be a variant spelling of Dalan meaning "corridor, hall" in Persian, a surname as well as a place name. There's also a village called Daylan Kandi in Iran though whether it's related to Dalan I can't say.
Daylan could also be a variant form of Dylan which means "great tide" or "great flow" from Welsh elements dy (great) and llanw (tide, flow) or Dillon.