"The tip-of-the-tongue (TOT) phenomenon is the feeling of knowing something that cannot be immediately recalled. TOT is a near-universal experience in memory recollection involving difficulties retrieving a well-known word or familiar name. Despite the word-finding failure, people have the feeling that the word to be remembered (the blocked word) is figuratively on one's "tip of the tongue." It is felt that the blocked word is on the verge of imminent discovery. Inaccessibility and imminence are two key features of an operational definition of TOTs."
Mentioned by Anton Chekhov in his 1885 short story, "A Horsey Name," but mentioned a lot earlier by Aristotle.
"Cognitive psychologist Bennett Schwartz examined fifty-one languages and found that forty-five of them include expressions using the word tongue to describe the TOT state. Some languages use multiple metaphors. In Korean, the metaphor "sparkling at the end of the tongue" is used, as well as "caught in the mouth and throat." French speakers use the "tongue" metaphor and the expression "memory hole". In some languages, eg. Danish, and possibly others as well, tongue is often replaced by lip, "I got it(word) right on my lips", the concept remaining identical, and having an obvious relation to the tongue. The results of the language survey suggest that the use of the "tongue" metaphor is not idiomatic to English but instead a commonality of the TOT phenomenon... TOTs occur most frequently for names of people, but for common words as well."
Thanks, Wikipedia! *salutes*