Shou ma7allo/a men el 2e3rab litterally means: "what's his/her grammatical function?" This question is used to ask who a person is or what kind of relationship a person has with another one.

Example:

- I saw you this morning walking on the street with a guy.
- Yes, that was Fadi.
- Aha, w chou ma7allo men el 2e3rab?
- Euh.... it's a friend I met at school.