alluvion vs multitude

alluvion

noun
  • The increase in the area of land due to the deposition of sediment (alluvium) by a river. 

multitude

noun
  • A great amount or number, often of people; abundance, myriad, profusion. 

  • The mass of ordinary people; the masses, the populace. 

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