water waggon vs waggon

water waggon and waggon both are nouns.

Word	Noun	Adjective	Verb	Adverb
water waggon	Yes	No	No	No
waggon	Yes	No	No	No

As nouns, waggon is a hypernym of water waggon; that is, waggon is a word with a broader meaning than water waggon:

water waggon: a wagon that carries water (as for troops or work gangs or to sprinkle down dusty dirt roads in the summertime)
waggon: any of various kinds of wheeled vehicles drawn by an animal or a tractor

Other hypernyms of water waggon include wagon.

water waggon (noun)	waggon (noun)
a wagon that carries water (as for troops or work gangs or to sprinkle down dusty dirt roads in the summertime)	any of various kinds of wheeled vehicles drawn by an animal or a tractor
	a car that has a long body and rear door with space behind rear seat