ETYMOLOGY
from Greek ἀδιάϕορ-ος (indifferent) + -ous
EXAMPLE
“…From all which may be inferred, that dissentions among the protestantes are not merely personall, or but pointes adiaphorous, indifferent, being as it were but peccant humors, and not true or formed diseases in their church, but they do concerne most profound doubtes of their religion, since otherwaies they would neuer anathematize, or condemne one an other with such acerbity of wordes…”
From: Whyte Dyed Black
Or A discouery of many most foule blemishes, impostures, and deceiptes
– Thomas Worthington, 1615
Lexicophilia 