Q: Why is it that “width” and “length” end in an “h” but “height” doesn’t? Were the last two words ever spelled “longth” and “highth”?
A: The noun “width” has a ring of antiquity to it, but it’s a relatively recent concoction.
The Oxford English Dictionary describes it as a “literary creation of the 17th century” that took the place of an older word, “wideness,” which (in various forms) dates back to Anglo-Saxon days.
It notes that the 18th-century lexicographer Samuel Johnson didn’t care much for “width” and considered the newbie “a low word.”
The OED points out the similarity of “width” to “breadth,” a 16th-century creation that replaced the earlier “brede,” which had roots in Old English.
And it notes the similarity of “breadth” to another term you asked about, “length,” which is an old word that may have influenced the creation of “width.”
The first published reference for “length” in the OED is from the Old English Chronicles, a collection of writings from Anglo-Saxon times.
The word has been spelled all sorts of ways over the years (lengthe, lenkith, leynthe, etc.), but I don’t see any evidence that it was ever properly written as “longth.”
(I got more than 59,000 hits for “longth” on Google, but most references to length seem to have come from non-native speakers of English. A Chinese manufacturer of scaffolding, for example, says, “The longth can be adjustable.”)
As for “height,” it is also a very old word and it was indeed originally spelled with a “th,” or rather with the Old English version of a “th,” called a thorn, which looked something like a “p” with both an upper and a lower stem.
The earliest versions of the word (using modern letters) included hiehtho, hehthu, and heahthu.
In Middle English, the form of the language spoken between 1100 and 1500, the thorn was often preceded by another archaic letter, the yogh, an early version of our “g.”
The Middle English spellings of the word (again, in modern letters) included heghthe and heighthe.
(In case you’re interested, I’ve written about thorns and yoghs before on the blog.)
I’m simplifying this quite a bit, but eventually, “th” replaced the thorn in southern England and “t” replaced it in the north.
Since 1500, according to the OED, the “t” versions of the word “have increasingly prevailed in the literary language” and the “height” spelling “has been by far the most frequent written form.”
I could go into this in greater length (or width), but I think I’ve hit the high points.