bathroom vs thunderbox

bathroom

noun
  • A lavatory: a room containing a toilet and (typically but not necessarily) a bathtub. 

  • A room containing a shower and/or bathtub, and (typically but not necessarily) a toilet. 

verb
  • To assist a patient with using the toilet and general personal hygiene. 

thunderbox

noun
  • Any lavatory or toilet, especially a rudimentary outdoor latrine or toilet, or an outhouse. 

  • A box of metal balls which is shaken to create a thunder sound effect. 

  • A chamber pot enclosed in a box; a portable commode. 

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