-ier Also -yer.
A person engaged in an occupation or activity.
[Either from Middle English, or via French -ier from Latin -arius.]
In examples from Middle English, the ending is a variant of -er1: glazier (Old English glæs, glass); brazier (Old English bræs, brass), a worker in brass. In words like carrier and occupier the ending is -er1 with the i converted from the final y of the stem. A few are spelled -yer, usually following a stem ending in w: lawyer, sawyer.
From the sixteenth century onwards, many French words ending in -ier have been brought into English: brigadier, cavalier, costumier, croupier, financier, fusilier, hotelier. See also -eer.