There is a famous story that claims that Coleridge wrote only the first part of “Kubla Khan”, due to an interruption. He conceived the full poem, complete, in a dream, wrote in a reverie, and lost everything after the fifty-forth line when a visitor from Porlock was announced and he was forced to raise his eyes from his page.
Reflecting on the process of writing, on the experience of being a writer, can be done directly or indirectly. It should not surprise if writers like to leverage a metaphor to express the feeling of being gripped and then abandoned by an idea, of clutching as you fall at something to which you were holding tight moments ago. Coleridge was describing an experience of writing, whether or not the person from Porlock was real.
My pet theory about “The Love Song of J. Alfred Prufrock” is that Eliot chose the name to have a sonic resonance for his audience with Coleridge’s visitor from Porlock, to ensure that his reported experience was in the back of the reader’s mind for the duration of the poem.
That is probably not all that revelatory a notion, but let me complicate things by adding a little bit about Dylan Thomas. The short story “One Warm Saturday” includes no explicit indication that it represents a dream. It begins in a very naturalistic setting, with a small-scale daytrip adventure, a visit to the seaside not unlike Prufrock’s. By the end of the story he has found and lost an unexpected girl. Lost because a call of nature, like Coleridge’s visitor or Eliot’s human voices, has pulled him out of the place where he knew where to find her.