ciao vs see you soon

ciao

intj
  • bye, goodbye. 

  • hello, hi. 

noun
  • A greeting or farewell using the word "ciao". 

see you soon

intj
  • goodbye; something said at a farewell, not necessarily literally meaning that the speaker will see the hearer(s) again. 

How often have the words ciao and see you soon occurred in a corpus of books? (source: Google Ngram Viewer )