loosen vs unloose

loosen

verb
  • To become loose. 

  • To make loose. 

  • To free from restraint; to set at liberty. 

  • To become unfastened or undone. 

  • To relieve (the bowels) from constipation; to promote defecation. 

  • To disengage (a device that restrains). 

unloose

verb
  • To become loose or come off. 

  • To loosen or undo (something that entangles, fastens, holds, or interlocks). 

  • To free (someone or something) from a constraint; (figuratively) to release (something which has been suppressed, such as emotions or objectionable things). 

  • To relax or slacken (something that clasps or grips, such as the arms or hands). 

  • To free from a constraint. 

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