Japanese uses both native and Chinese numbering numbering systems, the Sino-Japanese pronunciations being いち, に, さん, etc. and the native being hito, futa, mitu, etc. For the most part they are used for different things. However, numbers past 10 generally always use the sino pronunciations in modern Japanese, with some exceptions like 二十日 (はつか) or when fossilized in words such as 八百長 (やおちょう). To different degrees, Sino- and native numbering systems are also used in Vietnamese and Korean (and maybe others?). When did the Japanese start using Chinese numbers? When did native numbers past 10 fall into disuse?
八百長 (やおちょう) is one word, if you extract first two "八百", it will become "はっぴゃく" (meaning - 800) there is no relation between those two.
Regarding the word "八百長" timeline, Wikipedia, and Gogen guide, it started to be used in the Meiji Era (1868–1912).