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(What Has Been Seen) Cannot Be Unseen is an Internet axiom which states that one literally cannot get rid of the mental image that becomes part of the memory after looking at a disturbing photo or a video. The phrase is commonly used as incredulous reaction to a shock sites or a surprising revelation of anomalies in an unsuspecting image, similar to the usage of the phrase “when you see it, you’ll shat brix.”
The vividness of mental images in human brain has been studied by philosophers for centuries. While it is likely similar notions about our visual memory had been made before, the earliest known usage of the phrase “cannot be unseen” on the web can be found in an inspiring quote by Canadian cartoonist David Sim, which read:
“Once a profound truth has been seen, it cannot be ‘unseen’.”
Sim’s quote was cited in a number of blog posts and essays throughout the early 2000s. However, its first iteration in the context of describing a traumatic experience can be attributed to a personal blog post about Goatse titled “Some Images, Once Seen, Cannot Be Unseen,” written by Joey devIlla on December 15th, 2004.
Beginning in 2004, the phrase soon became associated with one’s reaction to seeing shock sites that were trending at the time. On November 3rd, 2005, the phrase appeared in a Tribe Magazine forums thread in describing the infamous Tubgirl. On September 24th, 2006, the phrase appeared in an eBaum’s World forum thread in which the OP asked other users to share some disturbing images that cannot be erased from their memories. The usage of the phrase became increasingly common in 2007, fueled by the creation of a demotivational poster featuring a picture of a wide-eyed cat and the phrase in caption.
On September 17th, 2007, it was mentioned in an inCrysis gaming forum thread to describe one’s first impression of 4chan. Later that same month, the phrase re-appeared on Neatorama as a comment in reference to the Tubgirl and in October 2007, the adage was brought up on the Internet humor blog Blame it on the Voices. The single topic blog Can’t Be Unseen was registered in September 2009, which focused on curating pairs of juxtapositional images to bring out a design flaw or a hidden imagery.
In 2010, several blogs began using the phrase as a tag for visually striking or odd images including the Daily What, Geekologie and Blame It On The Voices, not to mention the tag #cannot be unseen on Tumblr. In 2011, Buzzfeed also highlighted a series of images with the description “cannot be unseen.”
Search for the phrase began in October 2007, with “cannot be unseen” overtaking in popularity in November 2009. However, they both have similar search patterns, with matching peaks and drops.