head-on vs lineal

head-on

adj
  • Direct, abrupt, blunt or unequivocal; not prevaricating. 

  • Of a collision, from the front or in the direction of motion. 

adv
  • With the front of a vehicle. 

  • With direct confrontation. 

noun
  • A collision from the front. 

lineal

adj
  • In the direction of a line; of a line; of or relating to a line; measured on, or ascertained by, a line; linear. 

  • Composed of lines; delineated. 

  • Inheriting by direct descent; having the right by direct descent to succeed (to). 

  • Having an ancestral relationship to mothers, fathers, grandparents, (etc.) and having a descendant relationship to sons, daughters, grandchildren (etc.), exclusive of collateral siblings. 

How often have the words head-on and lineal occurred in a corpus of books? (source: Google Ngram Viewer )