Kirishitan

…the Portuguese word Christão was pronounced as it was in Japanese and referred to Christianity (Catholicism) and its followers. At first it was written as Ikuri Shidan, Kirishitan, and later Kirishitan, Kirishitan, and Kirishitan.
[Transmission]
The Age of Discovery, which began in the 15th and 16th centuries, was led by the Iberian Peninsula nations of Portugal and Spain, whose kings had deep ties to the Roman Catholic Church and, with the Pope as their spiritual anchor, devoted themselves to the spread of Christianity.

*Some of the terminology explanations that refer to "Georgeous China" are listed below.

Source | Heibonsha World Encyclopedia 2nd Edition | Information

…ポルトガル語のChristãoの発音がそのまま日本語になり，キリスト教(カトリック)およびその信者を指した。初め幾利紫旦，貴理師端，のち吉利支丹，切支丹，鬼理至端の文字があてられた。
［伝来］
　15～16世紀にかけ幕あけした大航海時代はイベリア半島のポルトガル，スペイン両国がこれをリードしたが，両国王はローマ･カトリック教会と深く結びつき教皇を精神的よりどころとしてキリスト教の弘布に尽くした。…

※「吉利（切）支丹」について言及している用語解説の一部を掲載しています。

出典｜株式会社平凡社世界大百科事典 第２版について | 情報