disencumber vs unlade

disencumber

verb
  • To remove an encumbrance or burden from (someone or something); unburden. 

unlade

verb
  • To disburden; take the burden from; relieve. 

  • To discharge a cargo; discharge a burden. 

  • To discharge the cargo from. 

  • To unload. 

How often have the words disencumber and unlade occurred in a corpus of books? (source: Google Ngram Viewer )