Think ‘yo!’ comes from a recent development in African-American vernacular? Think again. A multifaceted syllable bursting with history, there’s more to ‘yo!’ than meets the eye.
Some claim that the interjection was introduced into African-American culture through Basic Training in the US military during Vietnam or perhaps even WWII. “Yo!” would in this case be the equivalent of the response “Yes” or “Present”, perhaps altered for ease of enunciation in a very loud military voice.
Two decades ago however, a New York Times article claimed to trace it back to Italian immigrants in Philadelphia in the 1930s. ‘Yo!’ would be a shortened version of ‘guaglione’ (‘young man’ in Neapolitan), which made the shift through an approximate pronunciation of guahl-YO-nay>guahl-YO> whal-YO>Yo!.
Chapman’s dictionary of American slang dates ‘yo!’ to an exclamatory greeting used in the mid-19th century, but the word is attested as a sailor’s or huntsman’s utterance since c.1420. That’s right, ‘yo!’ was possibly being used to get someone’s attention back when Middle English was being spoken.
Some sources (notably wiktionary) claim that ‘yo!’ might also be related to Io! in Latin, which also appears in Ancient Greek as ἰώ (iō, “oh!”), and was used as an exclamation of joy or triumph. But here we would perhaps be taking things a little too far. As an interjection which rolls so easily off the tongue, it is very possible that ‘yo!’ has been reinvented through the centuries and millennia.
Today, you are as likely to hear ‘yo!’ in the lyrics of an east-coast rapper as you are to hear the word coming from the mouth of a president, like when George W. Bush greeted his long-term friend and Prime Minister of the UK with a friendly “Yo, Blair, what are you doing?” at the G8 summit in 2006… This became the butt of many jokes, and the the title of a book: “Yo, Blair!” by Geoffrey Wheatcroft.