latch vs unbolt

latch

noun
  • A breastfeeding baby's connection to the breast. 

  • A lightweight lock to protect internal structures from being modified by multiple concurrent accesses. 

  • A fastening for a door that has a bar that fits into a notch or slot, and is lifted by a lever or string from either side. 

  • An electronic circuit that is like a flip-flop, except that it is level triggered instead of edge triggered. 

verb
  • To catch; lay hold of. 

  • To close or lock as if with a latch. 

unbolt

verb
  • To unlock by undoing the bolts of. 

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