What does the word solem mean in old engilish?

The word "solem" is not an Old English word. It's a variant spelling of "solemn," which comes from the Latin word "solemnis" meaning "of a feast day."

In Old English, the closest word to "solemn" would be "gehalgod", which means "holy," "consecrated," or "sacred." This word was used to describe things that were set aside for religious purposes and considered to be special.

While "solem" itself isn't an Old English word, the concept of solemnity and the significance of special occasions were definitely present in Anglo-Saxon culture.