Learn Icelandic: Hann skammast sín fyrir dónaskapinn.

The verb skammast (to be ashamed) specifically requires its reflexive pronoun to be in the genitive case. While many reflexive verbs take the accusative (sig) or dative (sér), verbs like skammast take the genitive. For the third person (he, she, it, they), the genitive reflexive pronoun is always sín.

If I wanted to say 'I am ashamed of the rudeness,' would I still use sín?

No, sín is strictly for the third person. Because skammast forces the pronoun into the genitive case, you must use the genitive form of whatever pronoun matches the subject. 'I am ashamed' would be Ég skammast mín, and 'we are ashamed' would be Við skömmumst okkar.

Why does this sentence use the preposition fyrir instead of a word for 'of'?

In English, we say we are ashamed 'of' something, but Icelandic uses a different structure. The fixed prepositional phrase is að skammast sín fyrir eitthvað (literally: to be ashamed of oneself for something). You will frequently see fyrir paired with verbs describing emotions or reactions.

What case is dónaskapinn, and how is it formed?