鬼のいぬまに洗濯。

English Translation

When the cat’s away, the mice will play.

What?

“do laundry while the demon is away.”

As a proverb, it means to take advantage of an opportunity when the usually obstructive factors are absent.

I see. I was confused because I was taking いぬ to mean “dog,” but I suppose it’s a variant form of いない.

@cstuartroe
ぬ is one of the old Japanese conjugations we seldom use today. But you can still find ぬ in Samurai dramas and proverbs, etc. For example,

  1. Negation – Queen: Aren’t you coming? = そなたは来のか? = (modern) あなたは来ないのですか?
  2. Passive form – 『風立ち』(2013 Japanese historical drama film by Studio Ghibli) = “The Wind Rises” (the correct meaning is “The wind has risen.”)