man’youshuu
So, this word requires a little history and a little unpacking. 万葉集, or “collection of ten thousand leaves,” is one of Japan's most esteemed poetic anthologies. It was compiled around 759 AD during the Nara period (奈良時代). In all, there are about 4,500 poems, including 265 長歌, chouka, literally “long poems,” and 4,207 短歌, tanka, or “short poems.” The kanji here 歌 also means song. In terms of its literary qualities, the collection has been praised for hundreds of years for its sincerity and poignant writing style, which some scholars prefer to the more cultivated forms which appeared later in history.
Linguistically, one of the cool things about this collection is that it was written in 万葉がな man'yougana, which was the ancient Japanese writing system. Contemporary Japanese writing uses several scripts, two of which (ひらがな・カタカナ) are simplified phonetic derivatives of Chinese letters and one (the 感じ kanji) which are imported Chinese characters.
Man'yougana is exciting because it exists in the in-between stage of incorporating Chinese writing into Japanese. The poems inconsistently employ Chinese characters for either their pronunciation or their definition, so while they sometimes function to represent Japanese spoken syllables, other times they represent the traditional logographic meaning. This makes it a fascinating study because beyond being a gorgeous piece of literature, it is written in a really interesting intersection of culture and language.
The words break down very neatly, 万: ten thousand, 葉: leaf, and 集: collection, but I've really enjoyed looking through some of the interpretations of the phrase. Some scholars have connected the middle character to another Japanese word, 言葉 kotoba, a compound of the characters for speech and leaf which together mean "word." This imparts sort of a play on... words (haha) as in, the collection is like a tree with the poems and words in it as leaves. Additionally, others suggest that 万 man has a connotation of meaning something like "myriad, innumerable," so really it is implying that the collection is timeless and for all generations.