why everyone call me mamu[2]

so last time I told you all who called me mamu first time 

sorry for grammatical mistakes , I am not so absolute with rules but it's ok type 

let's continue with journey of being so called mamu 

as  Ritesh was first one to call me mamu 

so I thought he must have been joking by calling me mamu as only one meaning of mamu was known to me at  that time  

so I just wandered it as  his  mistake 

but he started me calling by same name time to time  I started feeling irritated by mamu name so I said  अबे मोटे क्या पागल तो नी हों गया है he said चुप बे मामू and I got to frustrated but I was in class  so controlled it  and just kept silence