It's not a whole onion on either side of pi. It's 1/5th of an onion (the "o") pi and then the other 4/5ths of the onion (the "nion") ....yes, I understood that, I just didn't write out that.. just the words I was seeing. onion pi onion still not ringing a bell. I guess I am just dense.
o - pi - nion
Yeah, not the best joke