water boy vs helper

water boy and helper both are nouns.

Word	Noun	Adjective	Verb	Adverb
water boy	Yes	No	No	No
helper	Yes	No	No	No

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

water boy: an assistant who supplies drinking water
helper: a person who contributes to the fulfillment of a need or furtherance of an effort or purpose

Other hypernyms of water boy include assistant, help, supporter.

water boy (noun)	helper (noun)
an assistant who supplies drinking water	a person who helps people or institutions (especially with financial help)
	a person who contributes to the fulfillment of a need or furtherance of an effort or purpose