An obvious nickname for the name Mallory is Mal but other names could be Malsy, Mally or Mal Gal but those are just for fun
More names:
Mal Pal
Malibu
Mallosaurus
mousy
Mal-mart
Malizipan
Mallaz
Alexander Mallory goes by Alex.
Noreen Mallory goes by Noe.
Troy Mallory goes by TC.
Mallory Swandar goes by Mal.
Mallory Woods goes by Executioner.
Mallory Escott goes by Mally, Malz, and Mal.
Boots Mallory's birth name is Mallory, Patricia.
Drue Mallory's birth name is Drue Mary Mallory.
Troy Mallory's birth name is Troy Christopher Mallory.
Mallory Swandar's birth name is Mallory Violet Swandar.
Mallory Ervin's birth name is Mallory Christina Ervin.
Mallory Cangialosi's birth name is Mallory Anne Prestlien.