Obiage is a type of small tool used when wearing kimono, and it wraps around obimakura (a small oval cushion to keep the obi (kimono sash) knot in place). Since it shows itself slightly out of obi, one often coordinates it with kimono or obi.
History of obiage is surprisingly short; it first appeared at the end of the Edo period. When Fukagawa geisha (geisha in Fukagawa, Edo (present-day Tokyo)) devised "taikomusubi" (a puffed-out bow of an obi), they also devised obimakura; it is considered that obiage was invented in order to hide the obimakura and to provide support for the obi which became heavier due to obimakura.
It is considered, based on the description of nishikie (colored woodblock print) and the like, that obiage became popular from around 1877. Commercialization of obiage was even later in history, probably around 1907 as can be speculated from newspaper advertisement and the like. According to advertisements by Mitsukoshi and Shirakiya department stores, it seems that the market price of one obiage was about 1.50 yen.
Typically, the formal attire on auspicious events is white, and the formal attire on occasions of mourning is black. Colorful obiage of complete tie-dyeing is said to be suited for furisode (kimono with long, trailing sleeves).
Also, it is said that only unmarried women can tuck in obiage in a manner which forms the character 入 when viewed from front (called "irikumi").