crab with little meat; crab of a moonlit night
Literal meaning: a crab caught on a moonlit night, which is said to have little meat. Used as the basis for the idiomatic sense.
It is said that crabs caught on moonlit nights have little meat.
something with no substance; all show and no substance
Idiomatic use: refers to something that looks impressive but lacks real content or value, like a crab with little meat.
His story was like a moonlit-night crab—there was nothing to it.
Standard kanji spelling for the idiomatic expression.
Variant with katakana for カニ, sometimes used for emphasis or in casual writing.
The expression originates from the belief that crabs caught on moonlit nights have less meat, possibly because they are more active and use up energy, or because the moonlight makes them easier to catch before they have fed well. The exact origin is uncertain.