This is the classiest kotowaza I’ve introduced yet, no doubt!
(He wo hitte shiri subomeru;
“Loosing a fart and [then] clenching your butt.”)
Locking the barn door after the horses are gone. This kotowaza refers to frantic attempts to fix or hide an error or embarrassment after it is too late to stop it from happening. The image is of someone trying to suppress a fart after it has already escaped. One of my sources claims that the saying is an admonition to admit your mistakes rather than trying to cover them up.
屁 (he, pronounced like “hey”) is a fart. (By extension, it can also mean “something worthless,” and there are a number of derogatory phrases and compounds that use this association, including 屁理屈 – herikutsu – “fart reasoning” – to indicate quibbling or sophistry.) Anyway, the 屁 is marked as the object of a verb by the direct-object marker を (wo). The verb in question is 放る (hiru). Normally this character is associated with the verb 放つ (hanatsu), “to release,” “to set free,” “to fire an arrow,” but with the hiru reading it specifically refers to expelling something from the body: flatulence, defecation, or giving birth. (Cf. the rough English-language idiom “poop out a baby.”)
放る is in conjunctive form, attaching it to the second half of the sentence, which is another object-verb pairing. The noun is 尻 (shiri), which as you might expect means “rear end” (I’m not just speaking euphemistically: a 川尻 – kawajiri – is the mouth of a river; a 目尻 – mejiri – is the outer corner of the eye). Here we skip a repeat of を, but its action is implied by the parallel structure. And finally the verb 窄める (subomeru), “to narrow (something),” “to fold (an umbrella),” “to purse (one’s lips),” in sentence-final form.
The verb 窄める can also be pronounced tsubomeru, although that reading seems to be less common for this saying. It is also acceptable to change the final verb to its imperative form, 窄め (subome). Some people apparently replace 尻 with 穴 (ana), “hole,” but this is considered incorrect.
Amazingly enough, this little gem also shows up in the Edo iroha karuta set. Its usage, in various forms, is attested since the mid-1600s.
「はい、宿題提出！」 「しゅ… ええと、宿題、ありましたか？」 「分かってるくせに！この前、君がちゃんとメモ帳に書いたのを見ていたぞ。ごまかしても、屁を放って尻窄めるに過ぎない」
(“Hai, shukudai teishutsu!” “Shu… eeto, shukudai, arimashita ka?” “Wakatteru kuse ni! Kono mae, kimi ga chanto memo-chou ni kaita no wo miteita zo. Gomakashitemo, he wo hitte shiri subomeru ni suginai!”)
[“Alright, turn in your homework!” “Home… um, there was homework?” “As if you didn’t know! I watched you write it down in your notebook. Trying to trick me now is just clenching your butt after the fart is out.”]