Did ありがとう come from Portuguese "obrigado"?


I have heard before that ありがとう came from the word "obrigado" in Portuguese. Is
this true and is there any evidence to support this, or is it an old wives'
tale?




It is false. ありがとう came from adjective ありがたい, which was ありがたし in classical
Japanese and dates back much earlier than any loanwords from Portuguese
appeared in Japanese.

Word ありがたし appeared in [Makura no
Sōshi](http://en.wikipedia.org/wiki/The_Pillow_Book) (1002), although I hope
that someone with access to large dictionaries can post earlier references.
Loanwords from Portuguese in Japanese started appearing in the 16th century.

_See also the comment to this answer by Dono. Honestly speaking, I think that
it is better than this answer._




It is false. ありがとう came from adjective ありがたい, which was ありがたし in classical
Japanese and dates back much earlier than any loanwords from Portuguese
appeared in Japanese.

Word ありがたし appeared in [Makura no
Sōshi](http://en.wikipedia.org/wiki/The_Pillow_Book) (1002), although I hope
that someone with access to large dictionaries can post earlier references.
Loanwords from Portuguese in Japanese started appearing in the 16th century.

_See also the comment to this answer by Dono. Honestly speaking, I think that
it is better than this answer._

