What does the old English word fen mean?

In Old English, the word "fen" simply meant "marsh" or "swamp". It referred to low-lying areas of land that were often waterlogged and covered in reeds and other water-loving plants.

The word "fen" still retains this meaning in modern English, though it's not used as frequently as it once was. It's often used to describe specific geographical areas, such as the Fens in eastern England, which are a large area of low-lying land that was once marshland.