Why is it that I can hear "Big Sis" used on Greek and not bat an eyelid, but the thought of using it for Marimite makes me cringe? They're the exact same sort of mentorship system, so it's as valid an English equivalent as it would be if they were actual sisters. Yes, it's casual, but it can also be affectionate, and I could see a formal speaker using it if it were a standardized part of the system. Maybe it's that I never actually heard it used that way until Greek (I've never been in a sorority and aren't close to anyone who is), which was only just recently, long after I first saw and read Marimite. Or maybe it just doesn't fit with the atmosphere at Lillian. Thoughts?