A class-mate in High-School once vented to me about how badly she hated it when she heard people pronounce the word “height” as if it ended with a “th”. At the time, I had only given serious thought to this matter once before (as far as I can remember), and that was in freshman English when we were assigned Great Expectations, in which Charles Dickens spells the word “heighth”. Although it crossed my mind that this might have been Dickens’ imitation of dialect (or, since I wasn’t really familiar with differences between dialects at this point, “regional bad grammar”), I was careful not to agree too quickly, knowing that his grasp of the English tongue was by all accounts superior to mine. But I have never been able to shake this from my memory, and since then I have heard other complain of this “error”. So which is right, “height” or “heighth”?
Of course, this being English, the answer is anything but simple. “Height” is the generally accepted spelling now, as you know and as my class-mate’s disgruntlement indicates. Advocates of this spelling argue that those who pronounce the word “heighth” are merely drawing a false correlation between “height” and words like “length” and “width”. They will, doubtless, be all the more disgruntled to learn that the correlation isn’t false. The word was originally “highth”. The “th” ending affixed to an adjective describing measurement really did change that word into a noun. Thus “highth”, “length”, “width”, and “breadth”, correspond to “high”, “long”, “wide”, and “broad”, respectively. In “heighth”, the “d” and the “th” presumably merged into the “t” in some dialects (leave a comment if you know which – I’d love to find out), which I guess was easier to avoid after the short consonant in “width”. In the meantime, “heighth” survived in colloquial use and has yet to be hunted to extinction.
If the vowel difference between “length” and “long” is bothering you, you might recall that the Old Norse cognate to the modern English word “long” was “langr”. As it happens, the Old English word was “lang”, just as it is in Scots (which has been strangely more conservative with English pronunciation than English has). This is one of a myriad of words spelled with an “a” in Old English that changed their spellings to “o” in modern English. “Ham”, for example, is the Old English word for “home”. (The Scots word is “hame”.) Now think about how much easier it is for that “a” sound to turn into either an “e” or an “o” than it would be for the “o” to turn into an “e”, things start to look moderately understandable.
I am not familiar enough with philologically chaotic Middle English period to tell you why, exactly, this change happened. I’m also not familiar enough with linguistics to tell you with any certainty why the older “lang” and “langth” weren’t both rounded into “long” and “longth”. In Old Norse, long consonants can result in the shortening of the vowel immediately before them. If this was true in English (which I think it might have been), then the “gth” at the end of “langth” would have shortened the “a” into an “e”. Since the Old English word for “broad” was “brad”, this would also explain the apparent discrepancy between “broad” and “breadth”, though the spellings do nothing that make this less confusing.
On another note, did you know that Iceland produces more bananas per capita than any other European country? I don’t know which part of that statement gives me more pause: Iceland’s superlative stance in the banana market, or the fact that Iceland is considered part of Europe.