What does "burg" mean?

Search: burg

Why: Williamsburg, Harrisburg, Wurzburg... I was thinking it was like "burb," but I just realized that isn't even the same word.

Answer: Fortress or walled town (in medieval Europe)

Source: Merriam-Webster

The More You Know: Sorta like borough, from Middle English burgh, from Old English burg, "fortified town;" akin to Old High German burg, "fortified place," and probably to Old English beorg, "hill."