The Collaborative International Dictionary of English v.0.48:

Disburthen \Dis*bur"then\, v. t. [imp. & p. p. Disburthened;
   p. pr. & vb. n. Disburthening.] [Cf. Disburden.]
   To disburden; to relieve of a load. [Archaic]
   [1913 Webster]