frivolous vs underhand

frivolous

adj
  • Silly, especially at an inappropriate time or in an inappropriate manner. 

  • Having no reasonable prospect of success because its claim is without merit, lacking a supporting legal or factual basis, while the filing party is, or should be, aware of this. 

  • Of little weight or importance; not worth notice; slight; trivial. 

underhand

adj
  • dishonest and sneaky; done in a secret or sly manner 

  • secret; clandestine 

  • thrown (etc.) with the hand brought forward and up from below 

adv
  • in a sly, sneaky or secret manner 

  • with an underhand movement 

verb
  • To trick, deceive or gull. 

  • To toss or lob with an underhand movement. 

  • To excavate downward in successive steps or horizontal slices while positioned above on unbroken ore. 

noun
  • The lower of two hands, the hand under the work. 

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