In 721 , he signed , with his mother Bertrada of PrÃ 1\/4 m , the foundation act of the Abbey of PrÃ 1\/4 m. The same year , also with his mother , he made a donation to the Abbey of Echternach . In 721 , Caribert signed , with his mother Bertrada of PrÃ 1\/4 m ( also known as Bertha or Beltrada of the Merovingians ) , the foundation act of the Abbey of PrÃ 1\/4 m. The same year , also with his mother , he made a donation to the Abbey of Echternach .