It is a brand name for Japanese tea (Uji tea) taken from Kisen's poem, "My hermitage is at the southeast of the capital, I live like this in the mountain away from the capital, and I turned myself in the mountain since I felt 'U' (hardship) at the everyday world, and that is why people call the mountain 'U'jiyama." It is also a slang for Japanese tea.
It is "Rokkasen Sugata no Irodori" chapter three.
Kisen (years of birth and death unknown, tradition unknown) was a priest and kajin in the early Heian period. He was one of the Rokkasen. Aside from the fact that he was a priest at Mt.Uji, there is no information about him, so there is nothing to be told today other than the following two poems. However, there are those who think that he was KI no Tsurayuki, after changing his name. In Kokin Wakashu Kanajo (Preface of Kokinwakashu written in kana by KI no Tsurayuki), his poems were described as follows. "The priest Kisen is unclear verbally, so the first and the last parts of his poems are not certain." "It is such as meeting clouds at dawn to see the autumn moon." "He composed few poems, so it is hard to know about him through his poems."
He was said to be the author of Kagakusho (a book on the study of waka poems) called "Wakasakushiki" (also known as "Kisenshiki"), but it is considered today to be an apocryphal book of the late Heian period.
According to "Mumyosho" (an essay on tanka poetry), the site of Kisen's residence can be found deep in Mimurodo of Uji City, and it is a must-see place for kajin. There is a small cave still left on a hillside called Kisen-do Cave.
The only two poems handed down to present are as follows.
(Ogura Hyakunin Isshu - the Ogura Anthology of One Hundred Tanka-poems by One Hundred Poets - Number 8)
My hermitage is at the southeast of the capital, I live like this in the mountain away from the capital, and I turned myself in the mountain since I felt 'U' (hardship) at the everyday world, and that is way people call the mountain 'U'jiyama (Kokin Wakashu 983 or Hyakunin Isshu - one hundred waka poems by one hundred poets).
I wonder if what I see from the trees is the light of a firefly flying about the valley or isaribi (a fire lit on a boat to lure fish) of a fisherman going out to the sea to catch fish (Gyokuyo shu 400, or Hikohimesiki/Kagakusho).