Is it farther or further?
early 14c., "den, cave," from Old English cofa "small chamber, cell," from Proto-Germanic *kubon (cf. Old High German kubisi "tent, hut," German Koben "pigsty," Old Norse kofi "hut, shed"). Extension of meaning to "small bay" is 1580s, apparently via Scottish dialectal meaning "small hollow place in coastal rocks" (a survival of an Old English secondary sense).
"fellow, chap," slang from at least 1560s, said to be from Romany (Gypsy) cova "that man."