grub vs true bug

grub

noun
  • An insect at an immature stage of its life cycle. 

  • Food. 

  • A dirty person. 

  • A despicable person; a lowlife. 

verb
  • To scavenge or in some way scrounge, typically for food. 

  • To dig; to dig up by the roots; to root out by digging; often followed by up. 

true bug

noun
  • Any of various insects of the order Hemiptera and in particular of the suborder Heteroptera, that are wingless or have two pairs of wings, and have mouthparts adapted for piercing and sucking. 

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