hairline vs sly

hairline

adj
  • very thin, as thin as a hair 

noun
  • A fishing line made from hair. 

  • The line along one's forehead where hair starts growing. 

  • A very thin line in writing, drawing, or typography. 

  • A very thin fissure. 

sly

adj
  • Light or delicate; slight; thin. 

  • Done with, and marked by, artful and dexterous secrecy; subtle 

  • Artfully cunning; secretly mischievous; wily. 

  • Dexterous in performing an action, so as to escape notice 

adv
  • Slyly. 

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