Keen Is An Anglicized Version Of The Popular Irish Boy’s Name Cian, Meaning “ancient.” Keen Is Also An English Surname, Which May Derive From An Anglo-Saxon Nickname Meaning “brave” Or The Old English Word kene, Meaning King. In Modern English, The Word “keen” Can Mean “eager Or Enthusiastic” Or “sharp; Highly Developed.” With So Many Positive Meanings, You Can’t Go Wrong With This Name For Your Little One!