body stocking vs undergarment

body stocking and undergarment both are nouns.

Word	Noun	Adjective	Verb	Adverb
body stocking	Yes	No	No	No
undergarment	Yes	No	No	No

As nouns, undergarment is a hypernym of body stocking; that is, undergarment is a word with a broader meaning than body stocking:

body stocking: a one-piece tight-fitting undergarment for women that covers the torso (and may have sleeves and legs)
undergarment: a garment worn under other garments

Other hypernyms of body stocking include unmentionable.

body stocking (noun)	undergarment (noun)
a one-piece tight-fitting undergarment for women that covers the torso (and may have sleeves and legs)	a garment worn under other garments