the shits vs diarrhoea

the shits and diarrhoea both are nouns.

Word	Noun	Adjective	Verb	Adverb
the shits	Yes	No	No	No
diarrhoea	Yes	No	No	No

As nouns, diarrhoea is a hypernym of the shits; that is, diarrhoea is a word with a broader meaning than the shits:

the shits: obscene terms for diarrhea
diarrhoea: frequent and watery bowel movements; can be a symptom of infection or food poisoning or colitis or a gastrointestinal tumor

Other hypernyms of the shits include diarrhea, looseness, looseness of the bowels.

the shits (noun)	diarrhoea (noun)
obscene terms for diarrhea	frequent and watery bowel movements; can be a symptom of infection or food poisoning or colitis or a gastrointestinal tumor