Oinureba onaji koto koso serarekere kimi wa chiyo mase kimi wa chiyo mase - Shui Wakashu(English Translation & Meaning)

老いぬれば同じ事こそせられけれ
君は千代ませ君は千代ませ

Roma-ji: Oinureba onaji koto koso serarekere kimi wa chiyo mase kimi wa chiyo mase
English Translation: When one has grown old
one cannot help but repeat
the very same thing:
may you live a thousand years,
may you live a thousand years.
Meaning: When one grows old, one cannot help saying the same thing over and over: may you live a thousand years, may you live a thousand years.
Commentary: Book Five Celebration Poems 271

Headnote: "Composed on the night when Fujiwara no Sanenobu came of age"
Joking that the old cannot help repeating themselves, the poet offers his congratulations on a coming of age by saying "may you live a thousand years" twice. Disguising the blessing as an old man's repetition, the wit reveals the warm good wishes of the aged poet. According to the headnote, it was composed on the night when Fujiwara no Sanenobu came of age. Sanenobu was a son of Fujiwara no Tamemitsu. The headnote in the source text gives the name with a different character, which appears to be an error for Sanenobu.
The author, written as Minamoto no Shitagō in kana, is Minamoto no Shitagō. Of the Saga Genji line, he took part in compiling the Gosenshū and in reading the Man'yōshū as one of the Five Men of the Pear Chamber. He is also known for compiling the dictionary Wamyō Ruijushō and is counted among the Thirty-Six Immortal Poets.

First line, "oinureba," means "once one has grown old," the perfective form with "ba" expressing a constant condition.
Second line, "onaji koto koso," means "the same thing," emphasized by the particle "koso."
Third line, "serarekere," means "one cannot help doing," with "rare" the continuative form of the spontaneous auxiliary "raru," and "koso" resolved by the perfective "kere." The poem pauses here.
Fourth line, "kimi wa chiyo mase," means "may you live a thousand years," with "mase" the imperative of the honorific "masu," a respectful form of "aru."
Final line, "kimi wa chiyo mase," repeats the fourth line exactly, enacting the very "same thing" of which the upper verse speaks.
Author: Minamoto no Shitagō
Source: Shui Wakashu
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