limerick vs tenson

limerick

noun
  • A humorous, often bawdy verse of five anapaestic lines, with the rhyme scheme aabba, and typically having an 8–8–5–5–8 cadence. 

tenson

noun
  • A form of lyric poem used by troubadours in Provençal in which two voices present different sides of an argument, in alternate stanzas, lines, or groups of lines with identical structure. 

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