fire watcher vs watcher

fire watcher and watcher both are nouns.

Word	Noun	Adjective	Verb	Adverb
fire watcher	Yes	No	No	No
watcher	Yes	No	No	No

As nouns, watcher is a hypernym of fire watcher; that is, watcher is a word with a broader meaning than fire watcher:

fire watcher: (during World War II in Britain) someone whose duty was to watch for fires caused by bombs dropped from the air
watcher: a guard who keeps watch

Other hypernyms of fire watcher include security guard, watchman.

fire watcher (noun)	watcher (noun)
(during World War II in Britain) someone whose duty was to watch for fires caused by bombs dropped from the air	a guard who keeps watch
	a close observer; someone who looks at something (such as an exhibition of some kind)
	a person who keeps a devotional vigil by a sick bed or by a dead body