Metal Gear Solid 2: Substance has a mode named "Zako Survival" in English, where the player faces off against successive waves of enemies that increase in difficulty, rank, equipment and tactical sophistication, keeping their items and equipment from one stage to the next, culminating with a final boss.
What is "Zako"? Is it based off a Japanese term for something like 'successive stages', or is it something else such as being named after a programmer/designer named Zako?
Hmm, this went a little deeper than I thought.
Zako (雑魚) is a Japanese word for tiny fish, 'small fry' as we might call them in English. Idiomatically, the term refers to weak people.
By extension, 'zako' has come to refer to carbon-copy enemies in video games or anime, the kind that rush the hero en masse to be cut down by the hero and/or player character. Synonyms for zako in this case include mooks, grunts and minions.
(Like a lot of things, the 'zako' terminology has been co-opted by the online fetish community, used to refer to groups of female soldiers soundly beaten by the heroes. Google at thy own risk.)
