English spelling is complicated, but it has its reasons for being that way. Given that it borrowed from other languages, pronunciation changes over time, and peculiarities in the evolution of printing standards all played a role in getting us to where we are today. The way a word is spelled tells a part of its history. But for a few words, the spelling gets the history totally wrong.
In the early days of printing, spelling varied a lot. As a standard began to develop in the 16th century, a fashion for all things classical led some people to look to Latin and Greek for spelling inspiration. So, for example, the word debt, which had been spelled dette ever since it had been borrowed from French that way, was gussied up with a silent b, the better to show its ultimate derivation from Latin debitum.
Many words were affected by this add-a-silent-letter trend. The changes, though fussy and unnecessary, did reflect distant historical roots. But sometimes they didn’t. Here are five weird spellings that came about through etymological mistakes.
Where did that sc in scissors come from? We used to spell it sissors or sizars. The classicizers of the 1500s thought the word went back to Latin scindere, to split, but it actually came to us (via French) from cisorium, "cutting implement." The same assumption turned sithe into scythe.
An unnecessary s was bestowed on iland in order to make clearer the link to Latin insula. Only island did not come from insula, but from the Old English íglund.
Ache is from an Old English verb acan. There was a related noun atche (other such pairs include speak/speech, break/breach, wake/watch). The spelling settled on ache under the mistaken belief that is was related to the Greek akhos (grief, pain).
In Old English the past tense of can did not have an l in it, but should and would (as past tenses of shall and will) did. The l was stuck into could in the 15th century on analogy with the other two.
When English borrowed soverain from French, it had no g. The word was formed after Latin superanus, "highest one" (from super, "above"). The word reign, however, coming from Latin regnare, did have a g in it, and it very easily made its way into sovereign.