Rashi on Genesis 5:29/רש"י על בראשית ה׳:כ״ט

1זה ינחמנו THIS WILL COMFORT US — He will ease from off us (ינחמנו) the toil of our hands. For until Noah came people had no agricultural instruments and he prepared such for them. The earth had brought forth thorns and thistles when they sowed wheat in consequence of the curse imposed upon Adam Harishon: in the days of Noah, however, this ceased (Tanchuma 1:1:11). This is what is meant by the word ינחמנו (viz., ינח מנו). If, however, you do not explain it in this manner, but from the root נחם “to comfort”, then the meaning you give to this expression (connecting it with the idea of “comfort”) will have no application to the name נח, and you would have to call him מנחם “Comforter”.