How did the "double consonant to shorten vowel" thing come about? ("furry" vs. "fury")

Question

In English, a doubled consonant most commonly means "shorten the previous vowel", where "shorten" means map phonemes like this:

• [aɪ] -> [i]
• [oʊ] -> [ɔ]
• etc

For example, fury is pronounced [fjʊri] but add another 'r' and you get [fəri].

Now, obviously this doesn't make much orthographic sense. So there must have been some historical reason for it. Anyone know?

Relatedly, when a [k] sound shortens the previous vowel, the doubling is not even written 'kk', but rather 'ck' ('cracking') - why? This feature is in many Germanic languages too.

Answer 1

"Furry" and "fury" is actually a pretty bad example of this rule because of what "r" does to vowels, and "u" in particular.

In any case, historically, a double consonant meant the consonant was long, which often meant the vowel was shorter to compensate. As English evolved, it lost phonemic consonant length, and compensated by latching on to the vowel length instead, hence the modern rule: doubled consonant means short vowel (ignore the Great Vowel Shift for the purposes of this discussion). The writers of English noticed this pattern and started applying it to (some) cases it never applied before, hence the doubling rule for inflections, to help distinguish from clipped silent E's.

As for "why ck", most words with a final /k/ are spelled with "c", and need the "k" when inflected to prevent the "c" from "softening" in front of the "e" or "i" in the ending. Also, it just looks nicer than "kk", and we have the option, so why not?

By the way, the double consonant rule is also where the "d" in "judge" comes from (and why I will never pronounce "kludge" with a long U, don't @ me): Because of the silent E, the "u" would be long, so the "g" must be doubled. But the "g" is also softened by the silent E, which means it's pronounced /dʒ/, so "gg" would suggest the wrong sound, but "dg" wouldn't.

Answer 2

Right,

This happens to be a very interesting question, unfortunately I think I can only help in part, but we'll see!

You're right, there is a historic reason for the differing orthography; if we look at the etymologies of the words, we find two very different historical roots. We will start (for no specific reason) with fur, whence inflected to form furry. We get our "fur" from the middle English furre and furren, which in-turn we obtained from the Old French "fuerrer" (where earlier writings replace the "ue" with an "o", but thats irrelevant here), the French may well have obtained this from the Old High German "fotar" (the most probable explanation for the earlier use of an "o" in the French) of little importance yet great interest, this comes from the Gothic for lining "fodr", anyway, the crux of it is: furry was never borne out of a linguistic rule upon inflecting fur, instead it was transported via its root from the Old French — fuerrer, I'm afraid I can't give you an answer as to why the Old French chose to duplicate the "f" found from the Old High German — only regional adoptions of OHG dialect will likely be responsible.

As for Fury, we again look to the French / Middle French, this time the word is "furie" but their scavenging is not from Old High German, as in the case of fur — instead from the Latin furia, this all boils down neatly to the Greek stem "thor" whence "thorub" (the former to hurry or rush, the latter a tumult). The transportation of the pronunciation along with the single "r" construction explains the classic rule's retention. fury {fjʊri}

Hopefully this goes some way if not all the way to answering your question.