Cian (KEY-in) is an Irish boy's name meaning "enduring, ancient." The most legendary namesake was Cian Mac Maelmuaid, son-in-law of Ireland's great Brian Boru, King of Munster. Cian led an army from Munster to victory against the Vikings during the Battle of Clontarf in 1014, where he and his father-in-law were killed in battle. Ironically, Cian's father Mael Muad had been killed by Brain Boru years before. In mythology, however, Cian is also known as Scal Balb and is father of Lug (Lugh, sun god) and son of Dian Cecht. In oral medieval narrative Cian's marriage to Ethniu was a romance/bridal quest. Today the most popular namesake is likely either Youtube star Cian Twomey or Kian Lawley.
In 2015 Cian was given to 153 boys, not too far outside the top 1000 but far enough from the top 100 to be unusual. It is currently a very popular name in Ireland, #14 as of 2015.
Spelled Kian the name is now Persian, pronounced key-AHN, possibly meaning "kings." (I say possibly because I believe this was actually the surname of the second dynasty of Persian kings. It also means symbol of pride or unity of the country, or essentially "united by one name" in Iran.) This is the case for Filipino-Iranian actor Kian Reza Kizemi and Iranian-American scholar and sociologist Kian Tajbakhsh, although it is possible they are named intently for the city Kian in Iran. However, the K spelling is used in Ireland as well, and currently ranks low in the top 100 there. Kian ranks inside the top 1000 at #487 and rising with 599 boys given the name. It also ranks in England, Wales, Netherlands, Scotland and Sweden. Geena Davis named one of her sons Kian. There's also model Kian Mitchum, Danish footballer Kian Hansen, singers Cian Morrin and Kian Egan, and British cyclist Kian Emadi. Keane is the Anglicized spelling of the Irish name. As Kiyan or Keyan it is also considered Arabic.