Many names or words with double letters or silent letters are just artifacts of a time when we either did pronounce the letters (knight was keh-nixt or keh-nicht, light was lixt), or have dropped letters from the word that used to be pronounced (plough became plow, but used to be pronounced like plug).
There are a ton of other reasons that a silent letter might pop up; letters that were **added for really no good reason** (the “u” in neighbour/honour in UK spelling), **to clarify an origin or meaning** (the s in isle was added to look like the Latin insula, and then later put in island for the same reason), **consonant clusters might just be pronounced differently in your region so they appear silent** (azma instead of asthma, or Chrissmus instead of Christmas) , **a letter may exist just to show it’s a version of another word** (the n in damn reflects it’s actually the shortened damnation, the g in phlegm reflects phlegmatic), and some other reasons as well.
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