Rupert Brooke wrote to a friend in 1914, and used the word
polypist. He wrote, "...so polypist and yet benevolent...". He added what to me was an amazing and
amusing note: "=of many faiths, not bespattered by a parrot, O Greekless!"

Did he make this word up, or perhaps mis-spell a real word?
I can't find it, nor come up with anything close to it.

This looks to be to be a home-made word, probably inspired by the epithet "papist" converted to a pun by substituting "poly" (many, diverse, varietous) for "pap" (referring to the Bishop of Rome). I especially appreciate the comment on parrot urine, however.

polypist was most probably composed from poly ( greek, =many) and pisteuo (greek,= I believe)

Thank you, wsieber! Certainly sounds likely.