Maundy vs observance

Maundy and observance both are nouns.

Word	Noun	Adjective	Verb	Adverb
Maundy	Yes	No	No	No
observance	Yes	No	No	No

As nouns, observance is a hypernym of Maundy; that is, observance is a word with a broader meaning than Maundy:

Maundy: a public ceremony on Maundy Thursday when the monarch distributes Maundy money
observance: a formal event performed on a special occasion

Other hypernyms of Maundy include ceremonial, ceremonial occasion, ceremony.

Maundy (noun)	observance (noun)
a public ceremony on Maundy Thursday when the monarch distributes Maundy money	the act of observing; taking a patient look
	conformity with law or custom or practice etc.
	the act of noticing or paying attention
	a formal event performed on a special occasion