連木で腹を切る
(Rengi de hara wo kiru; “To cut one’s belly with a wooden pestle”)

Definition:

An impossible event or task. By extension, attempting to achieve the impossible. Attempting a task that is as daunting as slicing one’s belly open with an object as soft, blunt, and rounded as a wooden pestle in place of a suitable tool like a blade.

Breakdown:

This is a pretty basic sentence. You’ve got the noun 腹 (hara), “belly,” which the particle を (wo) marks as the direct object of the verb 切る (kiru), “to cut,” which appears in sentence-final form. The particle で (de) marks the means by which the verb is performed – in this case, the noun 連木 (rengi). Note that 連木, not a common word, is often used to refer to a row of wooden crossbeams or posts (as in the photo below). In this case, however, it is the word in Kansai dialect for what is now more commonly known as a 擂粉木 (surikogi), a wooden pestle.

The kind of 連木 that this saying is NOT about. [Source]

For those unfamiliar with the terms: a mortar is a bowl for grinding things in, and a pestle is the rounded rod used to smash or grind the mortar’s contents. In Slavic folklore, the Baba Yaga is sometimes portrayed as flying through the air riding in a mortar which she “rows” with a broom and/or pestle.

This saying is the れ entry of the Kyoto and Osaka iroha karuta sets, where it appears without the particle を – an acceptable alternative form.

Example sentence:

「今晩精一杯頑張って、明日ちゃんと宿題を出しなさい。連木で腹を切るほど難しくないはずだよ」

(“Konban sei ippai ganbatte, ashita chanto shukudai wo dashinasai. Rengi de hara wo kiru hodo muzukashikunai hazu da yo.”)

[“Work as hard as you can tonight, and turn in your homework tomorrow like you’re supposed to. It’s not impossible.”]

From Neil Gaiman’s Sandman comic, issue #38, “The Hunt.” Gaiman seems to have liked Baba Yaga, because this isn’t the only time she shows up in his stuff.