Spelling pronunciation occurs when a word is pronounced according to its modern spelling and not the way it is traditionally pronounced. There are multiple reasons for such pronunciations to occur, including the addition of foreign words to a language and ignorance of the original pronunciation. Common features of pronouncing words as they are spelled is the inclusion of hitherto silent letters such as the ‘t’ in "often."
In English, spelling pronunciation occurred because of the clash between Old English and Norman French with their separate language structures and orthography. Old English spelled words how they sounded and pronounced every letter written. The Normans changed the spellings of words to fit the French orthographic system. Spelling pronunciation probably occurred when the changed spellings were encountered for the first time and spoken literally based on the English pronunciation system.
Taking the pronunciation of a word from its spelling should not be confused with spelling a word how it is pronounced. The latter is called pronunciation spelling, and as it is a reverse collocation, it is easily confused with spelling pronunciation. Pronunciation spelling is used usually when writing in dialect or when trying to capture an accent. Examples of this spelling change include ‘want to’ becoming ‘wanna’ and ‘going to’ becoming ‘gonna.’
'Clothes' is an example of a change in pronunciation based on the spelling. For generations, it was pronounced the same as ‘close,’ but later on, the written ‘th’ in the middle was added as a pronounced sound. The same occurred with falcon; the original pronunciation omitted the ‘l,’ but it later found its way into speech. The same rarely happens with regards to ‘salmon,’ where the ‘l’ remains largely invisible.
There are a number of differences between each dialect and each major or national form of English. Americans' pronounce ‘figure’ as a rhyme of ‘pure,’ but the British pronounce it as a rhyme of ‘bigger.’ American English tend to speak words with the ‘alm’ cluster as written, whereas British speakers pronounce it more traditionally, when it sounds like ‘arm.’
Other languages also have the spelling pronunciation phenomenon. Spanish takes words into its language often without changing their spelling or re-spelling so the spelling fits the sound. This has led to Rorschach being pronounced ‘Rorsas’ and Bach being pronounced ‘Bax.’ Japanese alters every foreign word that comes into its lexicon in two ways; it either forms a local pronunciation based on spelling or re-spells based on sound. Spelling pronunciation in Japanese has led to ‘symmetry’ becoming ‘shimetorii.’
Noah Webster and other American intellectuals and politicians advanced the idea of re-spelling all American words to fit their pronunciations. This idea would have done away with spelling pronunciation entirely, but would have also created a chasm between British and American versions of English. Webster and others believed a uniform and literal spelling system would aid foreigners learning English as a second language.