variant of -er1, usually in nouns designating trades: collier; clothier; furrier; glazier.
Origin of -ier1
a noun suffix occurring mainly in loanwords from French, often simply a spelling variant of -eer, with which it is etymologically identical (bombardier; brigadier; financier; grenadier); it is also found on an older and semantically more diverse group of loanwords that have stress on the initial syllable (barrier; courier; courtier; terrier). Recent loanwords from French may maintain the modern French pronunciation with loss of the final r sound (croupier; dossier; hotelier).
Origin of -ier2
Dictionary.com Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2019
suffix forming nouns
Word Origin for -ier
from Old English -ere -er 1 or (in some words) from Old French -ier, from Latin -ārius -ary
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
Online Etymology Dictionary, © 2010 Douglas Harper