Borrowing books, borrowing words
I was doing my semi-regular trawl through the bookshelves of charity shops yesterday, when I stumbled across a book on the "correct" pronunciation of commonly mispronounced words. I didn't buy it, in no small part due to the fact that I pronounce the letter R in many places where it said you shouldn't.
Anyhow, I did have a little flick through it and one example that caught my eye was the word niche. The book duly informed me that the common pronunciation was now neesh, although it used to be nitch.
This illustrates one of the biggest classes of historical mistakes in the development of modern English: inappropriate word borrowing.
Niche is a direct borrowing from French, with the spelling unaltered. But on the face of it, it's unpronouncable. The consonant cluster CH doesn't normally occur inside words unless it's part of TCH -- eg. itchy, ratchet etc. It occurs at the start of a word (chat, change, Charlie). The only words I'm aware of with CH (no T) at the end are sandwich and place-names ending similarly -- Norwich, Harwich etc..
The other problem with niche is that final E. Is it "Magic E" or not -- nih-tch or neye-tch?
Well what is magic E? It's that silent E at the end of a word that changes the sound of a vowel earlier in the word, but there's really no such thing. The rule is a little broader than that. Where the pattern is vowel-consonant-vowel, the first vowel is modified to sound the same as its name, so A goes from ah to ae, E from eh to ee, I from ih to eye etc.. However, where there are two or more consonants between the letter, this change is blocked -- eg to fit becomes fitting to preserve the original sound.
However, is CH really two letters? Linguistically, it's a digraph: two symbols representing one phonetic letter. As CH only occurs without T at the start and end of words, it's not something that we'd normally have to face. Thinking it through logically, words like fishing and without show us that similar digraphs are considered two letters, but the brain doesn't think like that.
Your brain cannot resolve the word niche on first sight against rules learned from other English words. That's why the pronunciation has reverted to neesh: it's a French word with a French spelling, so it only makes sense with the French pronunciation. Unfortunately, linguistic elitists saw fit to borrow the word whole-heartedly -- lock, stock, spelling and pronunciation -- rather than borrowing the pronunciation and writing it as though it was English: neesh.