initial vs liminal

initial

adj
  • Chronologically first, early; of or pertaining to the beginning, cause or origin. 

  • Spatially first, placed at the beginning, in the first position; especially said of the first letter of a word. 

noun
  • A distinguished initial letter of a chapter or section of a document. 

  • onset, part of a syllable that precedes the syllable nucleus in phonetics and phonology. 

  • The first letter of a word or a name. 

  • In plural, the first letter of each word of a person's full name considered as a unit. 

verb
  • To sign one's initial(s), as an abbreviated signature. 

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 initial and liminal occurred in a corpus of books? (source: Google Ngram Viewer )