(Toshiyori no hiyamizu; “Cold water for the elderly”)
This phrase describes a situation in which an elderly person is doing something more aggressive or showy, or even dangerous, than is appropriate for their physical condition. The image is of someone sufficiently advanced in years that they have lost some of their resistance to the cold, who nonetheless insists on bathing in, or even (gasp) drinking*, water that isn’t heated.
This relatively simple noun phrase centers on its final character, the noun 水 (mizu), “water.” This is preceded by the transitive verb 冷やす (hiyasu), “to chill [something],” in prenominal form.
Going back to the beginning, we find the noun 年 (toshi), “year.” This is followed by, and compounded with, the intransitive verb 寄る (yoru), “to approach,” or “to gather together,” also in prenominal form and acting as a noun. The compound 年寄り, perhaps prefixed with an お (o), is a polite term for “the elderly.” These two noun phrases are joined by the associative particle の (no).
Related phrases expand the list of things that old people shouldn’t do to include tree-climbing (木登り = kinobori), walking around outdoors at night (夜歩き = yoaruki), and boasting of one’s strength (力自慢 = chikarajiman). Closer to home, hiyamizu may be written as 冷水, without the intervening kana, without any change in meaning or pronunciation.
This is the to entry in the Edo iroha karuta set. It is attributed to a kabuki play titled 『善悪両面児手柏』 (Zen’aku ryoumen konote gashiwa).
* Multiple sources call out cold water as bad for drinking – and I made fun of this, above – but there is at least hypothetically a logical explanation: one source claims that the “cold water” in question was water taken from the Sumida River during the Edo period. Untreated water (especially from an urban waterway that contains a nontrivial amount of human waste, industrial waste, and garbage) can make you very sick, after all. While it was believed that water from the middle of the river was harmless, and young people could drink it without obvious harm, elders with relatively weak immune systems were in fact encouraged to boil the water first rather than using it “cold.”
(“Ano kyuujuunisai no obaasan ga furumarason wo hashitteru no wo mite, toshiyori no hiyamizu da to omotte fuan ni natta kedo, nanto, obaasan ga ore yori hayaku gooru ni tsuite genkisou de bikkuri shita.”)
[“I saw that 92-year-old woman running the marathon and it made me worry; I thought it was too much for someone her age. But, I mean, she finished more quickly than I did, and was still full of energy; it was quite a shock.”]