gens vs stratum

gens

noun
  • A legally defined unit of Roman society, being a collection of people related through a common ancestor by birth, marriage or adoption, possibly over many generations, and sharing the same nomen gentilicium. 

  • A tribal subgroup whose members are characterized by having the same descent, usually along the male line. 

  • A host-specific lineage of a brood parasite species.^([W]) 

stratum

noun
  • A class of society composed of people with similar social, cultural, or economic status. 

  • One of several parallel horizontal layers of material arranged one on top of another. 

  • A layer of sedimentary rock having approximately the same composition throughout. 

  • Any of the regions of the atmosphere, such as the stratosphere, that occur as layers. 

  • A layer of vegetation, usually of similar height. 

  • The level of accuracy of a computer's clock, relative to others on the network. 

  • A layer of tissue. 

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