Alison is primarily a female given name in English-speaking countries. It was originally a medieval French nickname for Alis, an old form of Alice derived with the suffix -on or -son sometimes used in the former French nicknames such as Jeanson ("little Jean") or Pierson ("little Pierre"). The Middle English form was Alisoun.
The variant spelling Allison is the most common form in the United States. Other variations include Alisson, Allisson, Allyson, Allysson, Alyson, Alysson, Alicen and Alycen, with nicknames Allie, Alley, Alie, Ali, Ally, Aly, Al, Aley and Alli.