I don’t remember the first time that I heard the phrase “birds of a feather flock together,” but I do remember hearing either that phrase or something like that phrase when I was young on a cassette tape called “Safety Kids” which was full of songs about learning to be safe.
Anyway, the meaning is very obvious. It means that people with the same interests will gather together. It doesn’t mean that people will always be in the same group, but that people will form groups based on interests.
Yet, this does nothing to explain the origin of the phrase. Some people think that it may have originated from around 380BC, but it seems that this was inserted by the translator.
Explaining the saying, though, is quite easy. Birds do tend to flock together. Ornithologists, people who study birds, explain this as a safety in numbers practice. Birds flock together in order to avoid being eaten by predators.
However, when it comes to language, it was more common to say “birds of a feather fly together” than “birds of a feather flock together.”
While the proverb was probably not around in 380BC, it was used as early as the 16th century. In 1545, William Turner wrote, “Byrdes of on kynde and color flok and flye allwayes together” in his papist satire, The Rescuing of the Romish Fox.
In 1599, the current known version is found in print in The Dictionarie in Spanish and English, compiled by John Minsheu, an English lexicographer. It says, “Birdes of a feather will flocke togither.”
As said previously, though, it was more common to use the word “fly” than to use the word “flock,” and it appears that way in 1600 in Philemon Holland’s translation of Livy’s Romance Histoire in 1600. It says, “As commonly birds of a feather will flye together.”
Curiously enough, the source that creates the idea that it may have been around since 380 BC is actually the most current of these sources making it seem quite obvious that it was not there, but instead inserted into Plato’s The Republic as “Men of my age flock together; we are birds of a feather, as the old proverb says,” by the translation by Benjamin Jowett in 1856. Also, other translations of Plato’s The Republic do not include the phrase, so scholars do not credit it as actually being there.
Martin, Gary. “Birds of a feather flock together”. The Phrase Finder. June 10, 2010 http://www.phrases.org.uk/meanings/birds-of-a-feather-flock-together.html>.