Japanese

wiktionary

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From Japan +‎ -ese.

etymonline

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Japanese (adj.)

1580s, Iapones; see Japan + -ese. As a noun from c. 1600; meaning "the Japanese language" is from 1828. As nouns Purchas has Iaponite (1613), Hakluyt Japonian. The destructive Japanese beetle attested from 1919, accidentally introduced in U.S. 1916 in larval stage in a shipment of Japanese iris.