just think about something they do a lot or that like makes them stand out. Incidents that may have happened. In my old sorority, Beta Mu Omicron (music service sorority), a girl in my pledge class got nicknamed Beaker because when she was in some science class she was checking out the hot teacher (she was a boy freak
and knocked over all the beackers on the table...thus she got named Beaker. My nickname was Lil Bit cuz Im petite
You want it to be something that kinda inside jokish too. Something that would need explaining. Here are some nicknames of my, well ex-sisters:
Stacey: Sweet Tea
Tiff: Wrong Turn/10-4
Tara: Barbie (we nicknamed her boyfriend Ken
Emma: Baba Liza (Its Romanian)
Amber: Giggles/Embryo
Kiana: Curley Q
Me: Nips/Pink Suga :P
Good Luck!