Jeggings are leggings which are styled to look like tight denim jeans, it is the blending of the word "jeans" with the word "leggings".
Jeggings（牛仔样式打底紧身裤）指看上去像紧身牛仔裤风格的打底裤，jeggings这个词就是jeans（牛仔裤）和leggings（打底紧身裤）两个词的合成词。

The 'j' not only refers to the appearance of denim, but also to the fact that they were first worn for jogging in early 2009.
这里的开头字母j不仅表示这种裤子的外形像牛仔裤，同时也表示这种裤子在2009年初出现的时候是人们在慢跑的时候穿着的。

Jeggings were brought on by the resurgence in style of skinny jeans in the mid- to late- 2000s, when a higher demand for even tighter style of pant came about.
Jeggings是在2000-2010年代中后期紧身牛仔裤再次流行的风潮下出现的，当时更加紧身的裤型需求量很高。

Since they are typically made of a denim/spandex blend and simply resemble regular tight pants, they are often worn on their own as opposed to under a skirt or dress.
由于当时的紧身牛仔裤是由牛仔布加氨纶的材料制成，而且与常规的紧身裤很相似，因此可以单独穿着，不用搭配裙子。

Some jeggings have faux zip-flies and pockets, while others just have an elastic waistband and no pockets.
有些jeggings会有假的拉链和裤兜设计，有些则带松紧腰带，没有裤兜。