What are "Kol ha'Sarim"?
'Rashi': They are singers. Song and lamentations are said in the same voice. Amos (8:9) said about this "v'Heveisi ha'Shemesh b'Tzaharayim v'Hachashachti la'Aretz b'Yom Ohr" ? this is the day of [death of] Yoshiyah. He died at 39, in the middle of his days ? "Yemei Shenoseinu Shiv'im Shanah" (Tehilim 90:10). It says "v'Hafachti Chageichem l'Evel v'Chol Shireichem l'Kinah? v'Samtiha k'Evel Yachid v'Acharisah k'Yom Mar" (Amos 8:10).
What became a statute?
'Rashi': When they have any pain and crying, they lament and cry over it, they mention this pain with it. This is like Tish'ah b'Av, on which we mention Kinos on those killed in decrees that occurred in our days. So they cry over the death of Yoshiyah. This is like "va'Tehi Chok b'Yisrael; ? Lesanos l'Vas Yiftach" (Shoftim 11:39-40).
What is "Kesuvim Al ha'Kinos"?
'Rashi': It is written in Sefer ha'Kinos 1 . Rashi (Eichah 4:1, 20), Malbim ? the fourth Perek of Eichah laments Yoshiyah, but includes the other Bnei Tziyon.
I.e. Megilas Eichah. It is not what we call nowadays 'Kinos. Yirmeyah wrote Kinah 11; the others were written much later, via R. Elazar ha'Kalir (some say that this is R. Shimon's son) and Rishonim! (PF)
