Rashi on Genesis 7:23/רש"י על בראשית ז׳:כ״ג

1וימח AND HE BLOTTED OUT — The word וימח is a Kal form and not a Niphal, and it is of the same grammatical form as ויפן and ויבן Every verb whose last root letter is ה, such as בנה, מחה, קנה when י and ו are perfixed, has Chireq as its vowel beneath the yod.

2אך נח means NOAH ONLY. This is its real meaning. But the Midrashic explanation is (Midrash Tanchuma, Noach 9) that he was coughing and spitting blood because of the trouble he had with the cattle and beasts (אך is taken as a מיעוט limitation, meaning to say that something is defective); others say, that he was once late in bringing food to a lion, so it struck him. Regarding him may the words be applied (Proverbs 11:31), “Behold, even the righteous is paid (for his evil deeds) in this world’’.