One of the mysteries of the English language finally explained.
Definition of principiation in US English:
principiation
noun
A starting or beginning. (a) The action or process of starting or originating something; (b) an instance of this; a thing which begins or originates, specifically a prefix. Now historical.
Origin
Early 17th century (in an earlier sense). From post-classical Latin principiation-, principiatio origination, derivation from first principles from principiat-, past participial stem of principiare + classical Latin -iō. In specific use in sense 2(b) after post-classical Latin principiatio prefix.