manner vs discourtesy

manner and discourtesy both are nouns.

Word	Noun	Adjective	Verb	Adverb
manner	Yes	No	No	No
discourtesy	Yes	No	No	No

As nouns, discourtesy is a hyponym of manner; that is, discourtesy is a word with a more specific, narrower meaning than manner:

manner (noun)	discourtesy (noun)
a way of acting or behaving	a lack of politeness; a failure to show regard for others; wounding the feelings of others
how something is done or how it happens	a manner that is rude and insulting
a kind	an expression of lack of respect