The use of a foreign saying within an English sentence

Hello,
Basically I am analysing captions within football (soccer) programmes over a period of fourty years. I have come across a specific caption within my research that I must include within my data-:

' "Grids" dances "pas de deux" as the ref looks on'

Firstly I was wondering what the use of the term "Grids" as opposed to his full name Phil Gridelet would be described as when analysing my piece for coursework. I understand that it can be looked upon as an abrieviation of the player's name,but it is also a nickname and I was curious as to whether or not there is a specific English Language word for this?
Also the inclusion of "Pas De Deux" within the sentence is obviously unusual, but how would I describe this as a English Language component.

[Casiopea]

Originally Posted by Lewis

"Grids" dances "pas de deux" as the ref looks on.

Firstly I was wondering what the use of the term "Grids" as opposed to his full name Phil Gridelet would be described as when analysing my piece for coursework. I understand that it can be looked upon as an abrieviation of the player's name, but it is also a nickname and I was curious as to whether or not there is a specific English Language word for this?

Also the inclusion of "Pas De Deux" within the sentence is obviously unusual, but how would I describe this as a English Language component.

Grids, without -s, would be a backformation:

Gridelet => Grid

But given that -s is not part of the name, that it's been added, Grids is most likely a diminutive suffix. Click here to read more about Diminutives in Sports. Grids is the diminutive of, or term of endearment for Gridelet.

As for the French phrase Pas De Deux, it's listed in the Oxford Dictionary of Current English; i.e., a dance for two, which makes it a borrowing, or a phrase borrowed (into English) from French.