Is Debussy's title et la lune descend sur le temple qui fut an allusion to a piece of poetry?

Yes, the title "et la lune descend sur le temple qui fut" by Debussy is an allusion to a poem by Paul Verlaine titled "Promenade sentimentale." Debussy often drew inspiration from poetry in his compositions, and in this case, he used Verlaine's imagery to capture a certain mood or feeling in his music.