casual vs on the surface

casual

noun
  • A person whose engagement with media is relaxed or superficial. 

  • A worker who is only working for a company occasionally, not as its permanent employee. 

  • A soldier temporarily at a place of duty, usually en route to another place of duty. 

  • A player of casual games. 

  • Shoes suitable for everyday use, as opposed to more formal footwear. 

  • A member of a group of football hooligans who wear expensive designer clothing to avoid police attention; see casual (subculture). 

  • One who receives relief for a night in a parish to which he does not belong; a vagrant. 

adj
  • Designed for informal or everyday use. 

  • Coming without regularity; occasional or incidental. 

  • Happening or coming to pass without design. 

  • Informal; relaxed. 

  • Employed irregularly. 

  • Happening by chance. 

  • Careless. 

on the surface

prep
  • apparently, outwardly; superficially 

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