The silent "u": "forty" and "fourteen"

Question

We all know that the cardinal and ordinal numbers 4 and 4th are spelled ‘four’ and “fourth” respectively. Then we have 14 and 14th which are spelled “fourteen” and “fourteenth”. Yet the numbers 40 and 40th are spelled without the letter ‘u’, as in “forty” and “fortieth”.

It is said that Old English and Middle English spelling was phonetic but over time letters were either added or removed from words to resemble more closely their Latin origins; e.g., dette was replaced by ‘debt’ (L. debitum). And as customs in pronunciation changed so did the spelling, for instance ‘drink’ used to be drincan in Old English.

With that in mind, it's not a surprise when the letter ‘u’ in fourty became silent, it was dropped.

Merriam-Webster says

The logical Middle English relic fourty, …, lasted until the 18th century, when for reasons unknown it fell out of use. Sometimes that's just how it goes in English.

However, the same spelling change did not happen to “four” /fɔː/, and "fourteen" /fɔːˈtiːn/ or /ˈfɔːtiːn/, despite the ‘u’ being also silent.

Is there an explanation for this discrepancy? Why did the spelling change for “forty“ but not for numbers “four” and "fourteen”?

Answer 1

It's just yet another weird illogical piece of English spelling. No logic to it at all.

In Anglo Saxon we had 4=feower 40=feowerti. Here you can see the "w" that became reduced to "u" in the modern spelling of four and absent from forty. Perhaps this follows the Northumbrian dialect "feuortig" in which the u/w has switched places with the "o". Perhaps it was one publisher in the 17th century that standarised on forty and the 18th century dictionary writers followed that lead. It is probably just random.

Det ->debt is special case. Generally the spellings became fixed, but the pronucniations changed. It is easier to understand Middle English when spoken than when written (for me anyway).

Answer 2

Two thoughts:

• "For" would look the same as the preposition "for", so would potentially be a little confusing in a way that "forty" isn't.
• Some speakers apparently say "four" differently from the "for-" of "forty". The Longman Pronunciation Dictionary by J. C. Wells gives only /fɔ:/ for British English but both /fɔ:r/ and /foʊr/ for American English. The OED specifies /fɔ(ə)r/ for American English. However, Wells doesn't give /oʊ/ as an option in the word "forty" (which he does for "fourteen"), nor does the OED include an optional schwa in "forty" (although the OED doesn't include an /r/ in "forty" either, so might have forgotten to include an American pronunciation at all in that entry).

It seems therefore that the "horse"/"hoarse" distinction that some speakers observe may involve different pronunciations for the vowels in "four" and "forty". This is also implied by the discussion at https://wordagents.com/forty-or-fourty/ .

Answer 3

Interestingly, forty is spelt differently from four and fourteen. There are good phonological explanations for this quirk. IIRC, at the close of the middle English period, forty had a diphthong [ou] which in Early Modern English merged with [o:]. [o:] was developed from middle English [ɔ:]. At that time, forty had two syllables due to which [o:] was shortened to [o] and manifested itself in the spelling; forty. Oddly enough, four and fourteen didn't undergo that shortening for some reasons. You may know that English spelling was standardised in middle English so it reflects that change.

In the seventeenth century [o] was lowered and lengthened before /‑r/ to [ɔː] coalescing in this position with the long vowel which only lowered before /‑r/ (i.e. to [ɔː]).

Here's what Eilert Ekwall has to say:

Before r-groups ME ō, ū have mostly been preserved as long vowels, EModE [u:], PresE [ɔ:], as in board, hoard, forth, mourn; a short vowel, however, in word, EModE [wurd], whence [wəːd]. A long vowel has been retained in fourth, fourteen, with EModE [oːu]; forty, on the other hand, had [ɔː] in EModE, whence through later lengthening [ɔː]. In words like earth, learn, beard, earn the pronunciation varied much in earlier ModE between long and short

("A history of modern English sounds and morphology" (page 12))