adj. sad
adv. sadly
n. sadness
v. to sadden

But I cannot celebrate his fall. Zu'u tiiraaz ahst ok mah. He was my brother once. This world will never be the same.
Zu'u tiiraaz ahst ok mah. = “I am sad at his fall.”
(Paarthurnax, 0009C20A)

I used to visit him from time to time. Nearly crazed by loneliness and captivity. Tiiraz [sic] sivaas. He did not even remember his own name.
Tiiraz sivaas = “sad beast”
(Paarthurnax, 00045D09)

Possibly from aaz ‘mercy’ and related words connoting pain.

Possibly from English ‘tears’. Misspelled as tiiraz in the dialogue.