These three words, for a long time merely literary, have gone out of fashion altogether except in compound use (“hitherto”, “hither and thither”) or when the writer or speaker wishes to introduce a whimsical note (“whither Obama now?”). It is a shame, because their loss also deprives us of shades of meaning.
The modern replacement for “hither” is simply “here”, doing away with the sense of movement. Consider these quotations from the dictionary: “Come hither unto me” (1550, and by the way “come hither” is still, just about, used adjectivally to describe a coy, arch, or seductive look bestowed by a woman); “hyther tendeth al prudence and pollycy” (1538). I believe that “hither” is the intensive form of “here”. The command “bring him hither!” implies “from that place to this” more imperiously than “bring him here!”
Likewise, “thither” intensifies “there” and “whither” intensifies “where”.
“Here”, “there” and “where” are ancient words, as one might expect of such important tokens of meaning. “Here” and “there” are closely related: the latter probably grew out of the former, a pleasing idea since we always start from “here”, unless of course we are Irish and giving directional advice (“I wouldn’t be starting from here”). “Where”, however, comes to us through the interrogative Anglo Saxon form “hwár?”, which is a relative of “hwā?”, “who?”
“When”, “what”, “where”, “who”, “why”, “which” and “how” all begin with aspirants. This somehow suggests, to me at any rate, the state of ignorance. When we are puzzled or confounded by something we often exhale through partially pursed lips. Might the initial aspirant have arisen, in the very deepest past, from association with this? After all, words have to begin somewhere. If they are onomatopoeic (e.g. “crow”, “crash”, “whip”) their etymology is easy to explain, but the expression of abstract ideas is so subtle that there must originally have been some common ground, however tenuous.
One of our vital abilities is to take things for granted. Without it we would never get anything done. Yet sometimes it is instructive to stop and consider an aspect – any aspect – of life to which we have never before given much thought. These three words, passing from use, remind us of the mutability and great age of our language, that gigantic construction built from nothing but a need to understand the other fellow and in turn tell him what we think. English is more than a means of communication: it is a teeming city, continually being redeveloped, partially demolished, rebuilt, the product of millions of minds and sensibilities.
Below the ground, slowly becoming buried by new layers of construction, the archaeology is there for anyone who cares to dig.