This often indicates a specific device, project, or batch. In professional archiving, these prefixes help identify the source of the data without needing to open the file.
Standard camera and system-generated filenames often follow specific patterns that act as a "digital fingerprint": mad025PKM_202912006.jpg
The "JPG" extension itself is a relic of 1990s computing. Early versions of MS-DOS and Windows had a three-letter limit for file extensions, forcing the "Joint Photographic Experts Group" (JPEG) to shorten its name to "JPG". JPG vs. JPEG This often indicates a specific device, project, or batch