It may grate on your sensibilities when people mispronounce words, especially people who should know better. However, the "correct" pronunciation may have been born of a mispronunciation long ago. Here are a couple of examples:
Words that used to begin with "n"
Adder, apron and umpire all used to start with an "n". Constructions like "A nadder" or "Mine napron" were so common the first letter was assumed to be part of the preceding word. Linguists call this kind of thing reanalysis or rebracketing.
When sounds swap around
Wasp used to be waps; bird used to be brid and horse used to be hros. Remember this when the next time you hear someone complaining about aks for ask or nucular for nuclear, or even perscription. It's called metathesis, and it's a very common, perfectly natural process.
There are many more ways that words changed, such as words that once had more consonants or vowels than they do today, which may explain why so many letters are silent (and why some words are hard to spell). There are terms for each of these different transformation processes, explained at The Guardian. You might want to keep them in mind the next time you are tempted to correct someone’s pronunciation. -via Boing Boing
(Napron shown available at the NeatoShop)