Saudi

wiktionary

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Borrowed from Arabic سُعُودِيّ‎ (suʿūdiyy), from سُعُود‎ (suʿūd), the name of the Saud family, who rule Saudi Arabia, and the adjectival suffix ـِيّ‎ (-iyy).

etymonline

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Saudi (adj.)

1933, from Sa'ud, family name of the rulers of Nejd from 18c. and of the kingdom of Saudi Arabia since 1932. The name is from Arabic sa'd "good fortune, happiness." With common Semitic national designation suffix -i.