I was reading a manga called Rengoku ni Warau and Kaishin said:
ったく、人をこき使いやがって
あのジジィほっつき歩いてやがる
Jisho says that こき使い means pushing someone around or to work someone hard but it doesn't seem to fit with the context. Kaishin said that to Goemon, a fellow ninja that was trying to convince him to desert the battlefield and who has been by Tanba's (ジジィ's) side for many years, so I don't think "pushing someone around" would be a good translation.
Moreover, I would like to know the origin of こき使い's こき.