During what decade did J.R.R. Tolkien use mythopoeia in his literary works?
The Silmarillion: The Silmarillion is a collection of mythopoeic works by English writer J. R. R. Tolkien, edited and published posthumously by his son, Christopher Tolkien, in 1977, with assistance from Guy Gavriel Kay. Mythopoeia:  This meaning of the word "mythopoeia" follows its use by J. R. R. Tolkien in the 1930s.
1930s