Hither is a rarely used adjective and adverb that has been largely replaced by here. It is correct, but somewhat old-fashioned, to say "Come hither," meaning "Come here," and "the hither side of the stream," meaning "the nearer side." Thither is an archaic word meaning "in that direction," "there," "toward that place": "I'll meet you on the thither side." Hither and thither appear with some frequency in the expressions "hither and yon," meaning "from here to over there," and "hither and thither," meaning "here and there."
Dictionary of problem words and expressions. Harry Shaw. 1975.