You shouldn't usually try to guess etymology based on superficial phonetic similarity, especially for such a common word. It is exceedingly unlikely that a country would adopt a language would just adopt a word for giving thanks (though there are exceptions).

Just for some fun of even greater coincidences between Japan and a Romance language, there are two almost identical words in Japanese and Romanian that have no etymological relationship: "sat" / "里" ("sa to") meaning village in both languages; and "baba" / "婆" ("ba ba") a derogatory term for an old woman in both languages ("hag").