piece of piss vs plain sailing

piece of piss

noun

  • Something easy to achieve. 

plain sailing

noun

  • Something that is simple, straightforward, or easy; something that offers no troubles or difficulties. 

  • The navigation of waters free from hazards or unfavourable winds. 

adj

  • simple, straightforward, or easy 

How often have the words piece of piss and plain sailing occurred in a corpus of books? (source: Google Ngram Viewer )