overswell vs spill over

overswell

verb
  • To swell or rise above (something, especially the rim of a container, the sides of something hollow, etc.). 

  • To cause (something) to be too swollen or large; to become too swollen or large. 

noun
  • An excessive or sudden increase or flood (of something). 

spill over

verb
  • (of a bad emotion, situation, etc.) to reach a climax 

  • to enter into another zone by way of accident or overcrowding; to overflow 

  • (of an infectious disease) to spread from one species of animal to another and particularly to humans 

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