The Collaborative International Dictionary of English v.0.48:

Disblame \Dis*blame"\, v. t. [OE. desblamen, OF. desblasmer;
   pref. des- (L. dis-) + blasmer, F. bl[^a]mer, to blame.]
   To clear from blame. [Obs.] --Chaucer.
   [1913 Webster]