The Collaborative International Dictionary of English v.0.48:

Onerate \On"er*ate\, v. t. [imp. & p. p. Onerated; p. pr. &
   vb. n. Onerating.] [L. oneratus, p. p. pf onerare.]
   To load; to burden. [Obs.] --Becon.
   [1913 Webster]