a suffix with the same meaning and properties as -an; -ian is now the more productive of the two suffixes in recent coinages, especially when the base noun ends in a consonant: Orwellian; Washingtonian.
Origin of -ian
extracted from L loanwords in which -ānus -an is joined to stems ending in i
Dictionary.com Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2019
Word Origin for -ian
from Latin -iānus
Collins English Dictionary - Complete & Unabridged 2012 Digital Edition © William Collins Sons & Co. Ltd. 1979, 1986 © HarperCollins Publishers 1998, 2000, 2003, 2005, 2006, 2007, 2009, 2012
variant of suffix -an used with stem endings in -i, from Latin -ianus (-anus). In Middle English, frequently -ien, from words borrowed via French.
Online Etymology Dictionary, © 2010 Douglas Harper