Translation of "Nagashibina" in Japanese

It is not known when the Hinamatsuri first started, but the Nagashibina, in its most primitive form, was already being celebrated during the Heian period.

ひな祭りがいつ頃からある祭りなのか、はっきりとはしていないが、平安時代にはすでに流しびなの原形があったようだ。