User blog comment:Thailog/Ep. 201 "Happy New Year!" discussion/@comment-70.135.107.234-20120430223025/@comment-4454131-20120501011332

it's because both groups were using the first few letters of the greek alphabet in order.

Alpha, Beta, Delta, Gamma etc. I just looked up the greek alphabet and it seems between Gamma and Zeta there's Epsilon but they seem to have skipped over that one.