discontinuity vs lacuna

discontinuity

noun
  • A lack of continuity, regularity or sequence; a break or gap. 

  • a subterranean interface at which seismic velocities change 

  • A point in the range of a function at which it is undefined or discontinuous. 

lacuna

noun
  • A small blank space; a gap or vacancy; a hiatus. 

  • Any gap, break, hole, or lack in a set of things; something missing. 

  • A language gap, which occurs when there is no direct translation in the target language for a lexical term found in the source language. 

  • An absent part, especially in a book or other piece of writing, often referring to an ancient manuscript or similar. 

  • A space visible between cells, allowing free passage of light. 

  • A small opening; a small pit or depression, especially in bone. 

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