Rain is heaven and earth is earth.
In the old days when there was no concept of the Earth, "Ametsuchi" meant the expanse of sky and earth that stretched out before one's eyes, in other words, the Earth itself.

The opening words of the Kojiki

As it says, "When Heaven and Earth began...", they respected this "Heaven and Earth", did not fear it, and lived side by side with it.
It is said that young girls of the Heian aristocracy had a custom of making a small bag called an "Ametsuchinobukuro" (a bag containing heaven and earth) at the beginning of the year, and sewing together the top and bottom of the bag, in the hope that the great deal of happiness placed inside would not escape.