fathom vs underseek

fathom

verb
  • To conduct an examination or inquiry; to investigate. 

  • To encircle (someone or something) with outstretched arms; specifically, to measure the circumference or (rare) length of something. 

  • To measure a depth; to sound. 

  • To measure the depth of (water); to take a sounding of; to sound. 

  • Often followed by out: to deeply understand (someone or something); to get to the bottom of. 

noun
  • Originally, the distance between an adult man's arms stretched out away from the sides of his torso so that they make a straight line perpendicular to his body, measured from the tips of the longest fingers of each hand, generally reckoned to be six feet (about 1.8 metres); subsequently used as a unit for water depth but now generally replaced by the metre. 

  • Depth of insight; mental reach or scope. 

  • An unspecified depth. 

underseek

verb
  • To examine; explore; investigate. 

  • To spend too little time or effort in seeking. 

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