Transferred use of the surname, which is from an Old English masculine personal name Cēolsige, derived from cēol ‘ship’ + sige ‘victory’. Its use as a girl's name may have been influenced by names such as Elsie. In the United States the spelling Kelsey is reserved chiefly for boys.
English: habitational name from places so named in Staffordshire and Sussex. The former was named in Old English as ‘open country (feld) where madder (mæddre) grows’, while the latter was named as ‘open country where mayweed (mægðe) grows’. The surname is now most common in Nottinghamshire.