Yo is an English slang interjection,[1] commonly associated with American English. It was highly popularized after being used commonly in Philadelphia, Pennsylvania since the 1970s.[2]
The term yo arose in Philadelphia and spread from there, after being commonly used among Italian Americans and African Americans in their Philadelphia, Pennsylvania communities.[2] It is used to signify informality, close cultural understanding, and to indicate communal bonding. It remains very popular among Philadelphia Italian Americans, possibly arising from the Italian language word io (meaning "I"). In Italian, first person statements are often proceeded by io, thus the yo at the beginning of sentences in Philadelphia may have evolved from this. There are various examples, however, of individuals of certain age groups adopting the use of yo as a greeting within their set. While this arrangement may have originated in inner-city areas and with persons of similar ethnic backgrounds, as the popularity of rap music and related culture spread, so did the usage of yo.
Although often used as a greeting, yo may come at the end of a sentence, often to direct focus onto a particular individual or group or to gain the attention of another individual or group. It may specify that a certain statement that was previously uttered is more important, or may just be an "attention grabber".
A famous example of a fictional Philadelphian bringing notice to the expression is Rocky Balboa, where the word is used throughout all of the films, and is part of the iconic line, "Yo, Adrian, I did it!", which was ranked 80th in the AFI's list of 100 best movie quotes.
In the Japanese language, the sentence-final particle yo is used to emphasize sentences as is often the case in English slang as above, but is etymologically unrelated. YŌ is also used by Japanese teens as casual greetings between friends, but is pronounced with a more drawn-out tone.