* From "Birmingham": The most straightforward explanation is that "Brummy" is simply a shortened and informal version of "Birmingham". This is supported by the fact that many place names are shortened in this way, such as "Londoner" or "New Yorker".
* From "Brummagem": Another theory suggests that "Brummy" comes from the old name for Birmingham, "Brummagem". This name was often used in the 18th and 19th centuries, particularly in a derogatory way. While it's uncertain if this was the direct origin of "Brummy", the association could have contributed to its use.
* From a local dialect: It's possible that the term "Brummy" originated from a specific characteristic of the Birmingham dialect. While this is less widely accepted, some speculate that it could be related to a unique pronunciation or slang word used by locals.
While the exact origins of "Brummy" are debated, it's clear that the term has been used for centuries to refer to people from Birmingham.