The phrase "slightly ajar door" is commonly associated with the works of Edgar Allan Poe, specifically his poem "The Raven." This phrase is used to describe the state of a door that is open just enough to allow a small amount of light to pass through, creating a mysterious and intriguing atmosphere. The origin of this phrase can be traced back to Poe's use of vivid imagery and descriptive language to enhance the mood and setting of his stories.

In "The Raven," the narrator describes the door as "slightly ajar" to emphasize the eerie and unsettling atmosphere of the room. This use of the phrase has since become a staple in literature and popular culture, often used to convey a sense of suspense or foreboding. The phrase's popularity can also be attributed to its simplicity and effectiveness in evoking a specific mood.

Data from various literary analyses and discussions on Poe's works support the idea that the phrase "slightly ajar door" is indeed from Poe's "The Raven." For example, a study by the Edgar Allan Poe Society of Baltimore notes that the phrase is used in the poem to create a sense of unease and anticipation, which are key elements of Poe's writing style. Additionally, numerous scholarly articles and books on Poe's work mention the phrase as a classic example of his use of descriptive language.

The phrase "slightly ajar door" has also been referenced in other literary works and media, further solidifying its association with the mysterious and eerie themes prevalent in Poe's writing. Its enduring popularity can be attributed to its ability to evoke a sense of intrigue and suspense, making it a memorable and effective literary device.