Nannie Doss: The Giggling Granny

Serial Killer, Nannie Doss, got her nickname from her smile and giggle during her confessions to police. The more she confessed to, the more she giggled.

Sources:
www.murderpedia.org
Criminal Minds-Wiki Fandom
www.encyclopediaofalabama.org
www.filmdaily.com
Black Widow by Ryan Green
The Giggling Granny: Serial Killer Nannie Doss by Annette Rice