The Collaborative International Dictionary of English v.0.48:

Cottier \Cot"ti*er\ (-t[i^]*[~e]r), n. [OF. cotier. See
   Coterie, and cf. Cotter.]
   In Great Britain and Ireland, a person who hires a small
   cottage, with or without a plot of land. Cottiers commonly
   aid in the work of the landlord's farm. [Written also
   cottar and cotter.]
   [1913 Webster]

WordNet (r) 3.0 (2006):

cottier
    n 1: a medieval English villein [syn: cotter, cottier]