(Yamiyo ni teppou;
“A gun on a dark night”)
Doing things at random without any clear plans or information. Taking shots in the dark without even a target, much less the ability to see and aim at one. Arbitrary, generally ineffectual activity. By extension, this phrase can also refer to a lucky hit; a fluke success where none could reasonably have been expected.
We begin with the noun 闇夜 (yamiyo), “dark night,” especially a moonless night, marked by the particle に (ni) as the location (or rather, the time) of an action. The verb itself is elided, but the action itself is suggested by the following noun, 鉄砲 (teppou), “gun.”
This is the や (ya) entry of the Kyoto iroha karuta set. Variants include the contracted 闇に鉄砲 (yami ni teppou) – which is the ya entry in the Osaka set – and 闇夜の鉄砲 (yamiyo no teppou), which makes the saying into a noun phrase rather than an implied sentence. Other variants replace the gun with 礫 (tsubute), a [thrown] rock, along with several different ways to express “darkness.” Replacing 闇夜 with 暗がり (kuragari), “darkness,” is considered an error.
Some uses follow this phrase with the elided verb, ～を撃つ (wo utsu), “to shoot [a gun].”
Compare and contrast the more-forgiving 下手な鉄砲も数撃てば当たる.
(“Ichiou, hitobanjuu yamiyo ni teppou wo utsu you na puroguramingu wo shita kara sofuto wa ugoiteiru keredo, kongo no debaggu wa hitsuyou fukaketsu da.”)
[“For what it’s worth, I spent the night coding without really knowing what I was doing and now the software runs, but it’s definitely going to need debugging later on.”]