c.1300, "pile, heap, or group of things," from Old Norse stakkr "haystack" (cf. Danish stak, Swedish stack "heap, stack"), from Proto-Germanic *stakkoz, from PIE *stognos- (cf. Old Church Slavonic stogu "heap," Russian stog "haystack," Lithuanian stokas "pillar"), from root *steg- "pole, stick" (see stake (n.)). Meaning "set of shelves on which books are set out" is from 1879. Used of the chimneys of factories, locomotives, etc., since 1825.
Very well-built in the sexual sense; having an attractive body, esp a large bosom: She's well-stacked and sort of young
[1942+; found in the form stacked up nicely at Stanford University in 1931]