Root of Paganism" when posting about Poul Anderson's The Broken Sword. Similar roots are to be found in Anderson's "Star Of The Sea":
"Trees of the grove were huge darknesses, formless save where boughs nearly bare tossed against heaven. Their creakings were like an unknown tongue, answers to the skirl and snarl of the wind." (Time Patrol, p. 494)
People imagine speech in the wind.
"...the wind in their treetops spoke with the voices of the darkling gods. Everard suppressed a shudder." (p. 510)
Even a time traveler from the twentieth century feels it.
"Niaerdh was in [the waves] with dread and blessing." (p. 583)
Persons naturally personify nature. A fictitious character is created by an individual author whereas a deity arises in the collective imagination.