A Commentary, Critical, Practical, and Explanatory on the Old and New Testaments, by Robert Jamieson, A.R. Fausset and David Brown  at sacred-texts.com
lam 5:1EPIPHONEMA, OR A CLOSING RECAPITULATION OF THE CALAMITIES TREATED IN THE PREVIOUS ELEGIES. (Lam. 5:1-22)
lam 5:2Our inheritance--"Thine inheritance" (Psa 79:1). The land given of old to us by Thy gift.
lam 5:3fatherless--Our whole land is full of orphans [CALVIN]. Or, "we are fatherless," being abandoned by Thee our "Father" (Jer 3:19), [GROTIUS].
lam 5:4water for money--The Jews were compelled to pay the enemy for the water of their own cisterns after the overthrow of Jerusalem; or rather, it refers to their sojourn in Babylon; they had to pay tax for access to the rivers and fountains. Thus, "our" means the water which we need, the commonest necessary of life.
our wood--In Judea each one could get wood without pay; in Babylon, "our wood," the wood we need, must be paid for.
lam 5:5Literally, "On our necks we are persecuted"; that is, Men tread on our necks (Psa 66:12; Isa 51:23; compare Jos 10:24). The extremest oppression. The foe not merely galled the Jews face, back, and sides, but their neck. A just retribution, as they had been stiff in neck against the yoke of God (Ch2 30:8, Margin; Neh 9:29; Isa 48:4).
lam 5:6given . . . hand to--in token of submission (see on Jer 50:15).
to . . . Egyptians--at the death of Josiah (Ch2 36:3-4).
Assyrians--that is, the Chaldeans who occupied the empire which Assyria had held. So Jer 2:18.
to be satisfied with bread-- (Deu 28:48).
lam 5:7(Jer 31:29).
borne their iniquities--that is, the punishment of them. The accumulated sins of our fathers from age to age, as well as our own, are visited on us. They say this as a plea why God should pity them (compare Eze 18:2, &c.).
lam 5:8Servants . . . ruled . . . us--Servants under the Chaldean governors ruled the Jews (Neh 5:15). Israel, once a "kingdom of priests" (Exo 19:6), is become like Canaan, "a servant of servants," according to the curse (Gen 9:25). The Chaldeans were designed to be "servants" of Shem, being descended from Ham (Gen 9:26). Now through the Jews' sin, their positions are reversed.
lam 5:9We gat our bread with . . . peril--that is, those of us left in the city after its capture by the Chaldeans.
because of . . . sword of . . . wilderness--because of the liability to attack by the robber Arabs of the wilderness, through which the Jews had to pass to get "bread" from Egypt (compare Lam 5:6).
lam 5:10As an oven is scorched with too much fire, so our skin with the hot blast of famine (Margin, rightly, "storms," like the hot simoom). Hunger dries up the pores so that the skin becomes like as if it were scorched by the sun (Job 30:30; Psa 119:83).
lam 5:11So in just retribution Babylon itself should fare in the end. Jerusalem shall for the last time suffer these woes before her final restoration (Zac 14:2).
lam 5:12hanged . . . by their hand--a piece of wanton cruelty invented by the Chaldeans. GROTIUS translates, "Princes were hung by the hand of the enemy"; hanging was a usual mode of execution (Gen 40:19).
elders--officials (Lam 4:16).
lam 5:13young men . . . grind--The work of the lowest female slave was laid on young men (Jdg 16:21; Job 31:10).
children fell under . . . wood--Mere children had to bear burdens of wood so heavy that they sank beneath them.
lam 5:14Aged men in the East meet in the open space round the gate to decide judicial trials and to hold social converse (Job 29:7-8).
lam 5:16The crown--all our glory, the kingdom and the priesthood (Job 19:9; Psa 89:39, Psa 89:44).
lam 5:17(Lam 1:22; Lam 2:11).
lam 5:18foxes--They frequent desolate places where they can freely and fearlessly roam.
lam 5:19(Psa 102:12). The perpetuity of God's rule over human affairs, however He may seem to let His people be oppressed for a time, is their ground of hope of restoration.
lam 5:20for ever--that is, for "so long a time."
lam 5:21(Psa 80:3; Jer 31:18). "Restore us to favor with Thee, and so we shall be restored to our old position" [GROTIUS]. Jeremiah is not speaking of spiritual conversion, but of that outward turning whereby God receives men into His fatherly favor, manifested in bestowing prosperity [CALVIN]. Still, as Israel is a type of the Church, temporal goods typify spiritual blessings; and so the sinner may use this prayer for God to convert him.
lam 5:22Rather, "Unless haply Thou hast utterly rejected us, and art beyond measure wroth against us," that is, Unless Thou art implacable, which is impossible, hear our prayer [CALVIN]. Or, as Margin, "For wouldest Thou utterly reject us?" &c.--No; that cannot be. The Jews, in this book, and in Isaiah and Malachi, to avoid the ill-omen of a mournful closing sentence, repeat the verse immediately preceding the last [CALVIN].