incipient vs liminal

incipient

adj
  • In an initial stage; beginning, starting, coming into existence. 

noun
  • A verb tense of the Hebrew language. 

liminal

adj
  • Of or pertaining to a beginning or first stage of a process. 

  • Of or pertaining to an entrance or threshold. 

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