oi vs wotcher

oi

intj
  • An informal greeting, similar to hi. 

  • An expression of surprise. 

  • Said to get someone's attention; hey. 

pron
  • I. 

noun
  • A working-class punk rock subgenre of the 1970s, sometimes associated with racism. 

wotcher

intj
  • A friendly greeting. 

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