sackage (n.)

1540s, "to plunder, (a place) after storming and taking," from French sac (n.) "bag," in the phrase mettre à sac "put it in a bag," a military leader's command to his troops to plunder a city (from or cognate with Italian sacco, which had the same meanings), from Vulgar Latin *saccare "to plunder," originally "to put plundered things into a sack," from Latin saccus "bag" (see sack (n.1)). The notion beneath the verb probably is "fill your bags with booty."

The U.S. football sense of "tackle the quarterback behind the line of scrimmage" (by 1969) probably is extended from the notion of "to plunder," though there may be a felt sense of "put in a bag involved. As a noun, "an act of tackling the quarterback for a loss," by 1972.