In hip-hop slang, the word shorty or shawty (the latter of which is derived from the Southern United States pronunciation), has multiple meanings. In the 1980s and 1990s, the word meant "newcomer", particularly a newcomer to rap music or to certain aspects of street life or gang life. It also simply referred to someone who was younger and greener than the speaker. More recently, however, the term has evolved to also mean a woman, especially an attractive woman. This more recent usage has been popularized by modern pop-influenced rap music.[1]
Shawty in slang can also refer to a young and attractive woman who is short. This is one of the reasons it sounds like the word 'shorty'. Justin Bieber uses this phrase often in his songs along with other singers or rappers mainly from the USA.