The word "spell" has a long and complex history, and its origins can be traced back to several Old English and Middle English words. The modern English word "spell" is derived from the Old English word "spellian," which means "to tell or speak." This word is related to the Old English word "spel" or "spele," which means "a tale" or "a story."

The Old English word "spellian" was used to describe the act of telling or speaking a story, and it was often used in the context of magic or incantation. In Middle English, the word "spell" began to take on the meaning of "a magical or mystical utterance" or "a charm or incantation." This meaning was likely influenced by the Old English word "spel," which was used to describe a magical or mystical ritual or ceremony.

Over time, the meaning of the word "spell" has evolved to include a wide range of related meanings, such as "a set of words or letters used to achieve a specific purpose" (as in a magic spell or a spell of illness), "a specific period of time" 

 Why words like thee or thou are not used anymore