Two Kokin wakashū poems that start the same way, by two poetry immortals.

The first is by FUJIWARA no Okikaze, and the second is by KI no Tsurayuki (who was the chief editor of the 'Shū and wrote its Japanese introduction).

君こふる　涙の床に　みちぬれば　みをつくしとぞ　我はなりける

kimi kohuru/ namida no toko ni/ mitinureba/ mi wo tukusi to zo/ ware ha narikeru

君こふる　涙しなくは　からごろも　むねのあたりは　色もえなまし

kimi kohuru/ namida sinakuha/ karagoromo/ mune no atari ha/ iro-moe namasi

Kimi kohuru namida: [the] tears [I weep in] loving you. Koi (恋) the noun actually derives from an archaic verb, kohu, and that's what we see here.

The first poem says that the tears "have filled the floor, and I have exhausted myself, like the exhaust from a jet-ski racing down the resultant river of tears. Also, I touch your arm."

The sharp-eyed reader will notice that my translation is quite free here; in fact, jet-skis were not introduced to Japan until the Kamakura period, several centuries after this poem was written. The original relies on an untranslatable and unforgivable pun on mi wo tsukusu (exhaust oneself, squeeze oneself dry) and miotsukushi (a guidepost indicating the recommended current to use on a river*).

So the gist is, "I cried a river over you, and now I'm lying in it like a guide post. Hey, that rhymes with 'I exhausted myself because I cried most!'" ... Let's move on.

The second poem takes a different approach. Rather than elaborating on the tears themselves, it makes claims about what would happen if the narrator weren't weeping them: the chest area of his clothing would burst into colorful/passionate flames.

(I love this poem because it evokes a Heian noble blinking fiercely and claiming that he has something in his eye, right up until he spontaneously combusts. It's not good to keep these things bottled up.)

The really intriguing phrase, though, is iro-moe. I can't find any reliable commentator willing to state that they are 100% certain what it means, but it probably has to do with the color (iro) of the blaze (moe-), or its passionate (iro, cf modern iroke etc.) nature, or both.