出典:Wiktionary
From Middle English -eys, from Old French -eis, from Latin -ēnsis (in some cases from Late Latin -iscus). Compare Italian -ese.
-ese
Generally speaking, nouns formed with the suffix -ese have no distinct plural form (two Viennese) and, with the definite article, are plural and refer to an entire group (the Ravennese). They are also generally not used in the singular, as in "I am a Chinese"; instead, phrases like "I am a Chinese person" are used. (In some British dialects, "a Chinese" can be used, but to refer to a Chinese meal, rather than a person.) This is not always the case, particularly for speakers from East Asia who use it to translate demonyms such as 日本人 and 中国人, but such countable uses may have nonstandard meanings.