See studies by K. Ryan (1994), C. Byrnes (1995), J. Slay, Jr. (1996), C. Byrnes (2002), D. Malcolm (2002), and P. Childs, ed. (2005).
"Ian" or "Iain" ([ˈiːʲən]) is the Scottish Gaelic version of John. It is a very common name in much of the English-speaking world. In the United Kingdom, Ian was the 19th most common male name, taking account of the whole population (over 300,000 Ians in total). Although it disappeared from the top 100 male baby names in the UK, it is now becoming more popular in the USA, currently at number 68 in the baby name charts.
In Scottish Gaelic, this is the common form of the name "John", and is often spelt with two "i"s. In the Bible, "Eoin" is used. Other Gaelic forms of "John" include "Seonaidh" ("Johnny" from Lowland Scots), "Seon" (from English), "Seathan", and "Seán" and "Eoin" (from Irish). In Greek 'Yanis' or 'Ianis' or 'Ioannis' is a particularly common name.