Help with Charter from 1150

Hi

I am carrying out some family research and have come across some text that I feel is important and I cannot afford to missunderstand the wording.

The background is, in the Charter a man named Robert Mallet is giving land to this person before the persons name there is this text… Malus Nepos.

My take on this text is that the person is Robert Mallets Grandson but why use the word Malus rather than Mallei. The Malus word is used three times later in the charter for different people so I know that its not a Clerks error.

I would like to understand why the scribe used the word Malus

Any assistance will be much appreciated.

I did wonder if the Malus Nepos signified that the person was related by blood but illegitimate - Bad Grandchild.

I’m wondering if it isn’t simply a Latinized version of the name:

https://tinyurl.com/va8z7xc

Thank you for your reply, I did wonder if the Malus was somehow Malet but why use the word Malus rather than Mallei, Malus is such a bad word to use, in more ways than one.