derived from the spelling
of a word, and disregarding the traditional pronunciation. The result might come across as ignorance
, or it might become established as a or the valid pronunciation.
Children learn their spoken language long before they know how to spell, even in the most literate societies, so sound change normally happens without regard to the written form, and spelling lags behind. In the case of the notoriously irregular system of English, the spelling rules largely originated in the Middle English period (c. 1150-1450), but major changes in pronunciation have taken place since then.
The effect is often to reverse a previous change in pronunciation. For example the words London, waistcoat, forehead, often historically came to be pronounced Lunnon, weskit, forrid, offen. But they later came to be re-pronounced with the letters in their original spelling. The change from Lunnon to Lundon is reported in polite speech from around 1820, and Lunnon is now regarded as sub-standard. With the other three words, both pronunciations are current.
Because variant pronunciations can co-occur, with one being standard and the other dialectal or belonging to some other less visible lect such as lower-class speech, it is possible that the apparent change is actually a case of the older pronunciation not being re-created anew but becoming more acceptable and visible.
Particularly in English and French, scholars in past ages have introduced silent letters as a marker of etymology. For example, det and suttle acquired a B because their Latin roots had a B. Sometimes these scholastic additions to spelling have influenced the pronunciation: author (from Middle French autor), fault (from faute).
Examples of spelling pronunciations that haven't taken off include those formed by wrong segmentation, such as saying misled as mizzled, seeing it as from a verb misle; and being puzzled by an unfamiliar learned word, such as seeing epitome as EP-i-tome. Usually it is just a matter of subsequently learning the standard correct pronunciation. However, the reinterpretation can take off: some people pronounce the first word in double entendre as English double rather than the French monosyllable doobl.
ponder gives me a nice example: Mikhail Gorbachev at Live Aid in 1985 spoke of the underfed as if someone hadn't derfed them.