tern vs threefold

tern

adj
  • Consisting of three components; ternate, threefold, triple. 

noun
  • A thing with three components; a set of three things. 

  • Any of various seabirds of the subfamily Sternidae (of the family Laridae) that are similar to gulls but are smaller and have a forked tail. 

threefold

adj
  • triple 

  • three times as great 

verb
  • To make threefold; to triple. 

noun
  • An algebraic variety of dimension 3. 

adv
  • by a factor of three 

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