hip-hop slang, "great, excellent," 1992, originating perhaps in the late 1980s and meaning at first "sexiness in a woman." The word itself is presumably a variant of fat (q.v.) in one of its slang senses, with the kind of off-beat spelling preferred in street slang (compare boyz). The spelling is attested as far back as 1678, as an erroneous form of fat (a classical over-correction; see ph).
In the modern word it is said by some to be an acronym, and supposed originals are offered: "pretty hot and tasty," or "pretty hips and thighs" among them, all unconvincing. These may have begun as improvised explanations to women who felt insulted by the word.