clan vs gens

clan

noun
  • A group of people all descended from a common ancestor, in fact or belief, especially when the exact genealogies are not known. 

  • A traditional social group of families in the Scottish Highlands having a common hereditary chieftain 

  • Any group defined by family ties with some sort of political unity. 

  • A group of players who habitually play on the same team in multiplayer games. 

  • A badger colony. 

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]) 

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