Prof Andrew Gerstle teaches pre-modern Japanese texts at the University of London.
He explained to the BBC the term might be older than you think – it can be found in print as early as 1879, meaning it was likely in use before that.
The word “doku” can be used as a verb to mean “reading”. According to Prof Gerstle, the “tsun” in “tsundoku” originates in “tsumu” – a word meaning “to pile up”.
So when put together, “tsundoku” has the meaning of buying reading material and piling it up.
“The phrase ‘tsundoku sensei’ appears in text from 1879 according to the writer Mori Senzo,” Prof Gerstle explained. “Which is likely to be satirical, about a teacher who has lots of books but doesn’t read them.”
While this might sound like tsundoku is being used as an insult, Prof Gerstle said the word does not carry any stigma in Japan.