八雲立つ: Yakumo tatsu, the opening words of the poem called the first waka

そこで歌うたった「八雲立やくもたつ」で始はじまる歌うたは、最初さいしょの和歌わかといわれています。

The poem that begins with the words “Yakumo tatsu,” which he sang there, is said to be the first waka.