What is "Techon"?
Rav Sadya Gaon: It is a Kli that grinds [spices].
Rashi: It is a mill. When the enemy led them in nooses, they put on their shoulders mills and loads in order to weary them.
Ibn Ezra: It is Makor 1 (like an infinitive); they carried (took) Bachurim to grind.
Rid: They forced Bachurim to grind.
Ibn Ezra: Also "Nil'eisi Neso" (Yeshayah 1:14) is Makor.
What is the significance of "ba'Etz Kashalu"?
Rashi (from Eichah Rabah 5:13): Their strength weakened via [carrying] wood. Kishalon applies to weakness - "Kashal Ko'ach ha'Sabal" (Nechemyah 4:4), "Hichshil Kochi" (above, 1:14).
Ibn Ezra #1: The strength [of the Bachurim taken to grind] when they needed to move the wood that grinds.
Ibn Ezra #2: They made Bachurim carry mills and wood [and this weakened them]; every camp needs them.
Ri Kara: Bachurim were forced to carry mills, and youths to carry wood.
Rid: Youths stumbled while working with wood.
