The name colleen is of irish origin and is derived from the irish word cailín, which means girl or young woman. it is a diminutive form of the irish word, emphasizing youth and endearment.Colleen is an english-language name of irish origin.It derives from the irish word cailín girl/woman, the diminutive of caile woman, countrywoman.Colleen milroy is board certified in obstetrics, gynecology, reproductive endocrinology and infertility with more than 10 years experience.