Hie has been part of English since the 12th century, and it stems from the even hoarier hīgian, an Old English word meaning "to strive" or "to hasten." Hie enjoyed a high popularity period from the 16th to the 19th centuries, and you're sure to encounter it in the literature of those times—writers from Shakespeare to Twain penned it into their prose. But don't get the idea that hie is just a word of the past; it regularly pops up in current publications as well—often, though not always, in contexts in which the author is wanting to approximate an old-timey way of communicating.