It has been claimed by a reliable source (Fayce-Booke, 2018) that no Germanic language truly has vowel-initial words; rather, all the words we think start with vowels actually start with a glottal stop. Examining the empirical truth of this claim is beyond the scope of this paper; rather, I will seek to explain why.
As the anthropological saying goes, anything in a culture that can’t be easily explained must have a religious or ceremonial function (Some Blog Comment or Something I Read Once, n.d.). Similar reasoning applies to sound changes: if we don’t know why a word changed in sound as it did, the answer must be taboo deformation. In this process, the sound of a word is changed in unruly ways because the word itself denotes something forbidden (sexual and/or scatological and/or sacred and/or scary), or because it sounds too much like a taboo word.
But why would all words beginning with vowels be tabooed? I believe the answer lies in the word “vowel” itself—as I have recently discovered by making some rather embarrassing typographical errors, it is awfully close to both “owl” and “bowel.” The former is a bird of ill omen, and the latter is a really icky body part. To ʔallow ʔa vowel to head ʔa word, without ʔa safely ʔinsulating consonant, would be to ʔinvite despair, dysentery, ʔand raptor ʔattacks.
So why ʔis this ʔall-ʔimportant ʔinitial consonant no longer part ʔof the ʔorthography? Because ʔuneducated readers would ʔoften mistake ʔit for ʔa question mark, leading them to ʔadopt ʔa strange form ʔof, like, ʔuptalk when reading ʔaloud. Which listeners found really ʔannoying. With the advent of antibiotics and the decimation (in the colloquial sense) of many bird-of-prey populations in Europe, the ancestral ornithological and gastrological curses were less of a concern anyway. But echoes of this tradition can be seen in the new language developed by millennials, whom as we all know communicate largely through disemvowelled txt-spk and emojis.
And why specifically a glottal stop? I suspect that its apotropaic function comes from being a mimesis of the process of ejecting distasteful food from the oral cavity (always a serious consideration in Britain). Therefore, to produce this sound before a vowel was to symbolically reject and spit out the accursed thing, negating its bird-summoning, intestine-upsetting power. One is tempted to suggest, furthermore, that the glottal stop emerged as a mimicry of sounds made by corvids, traditionally enemies of owls, but that would be ridiculous.