Many DVR and NVR systems (like those from Lorex or Swann) use alphanumeric prefixes like "g" followed by a channel number and sequence to name exported clips.
Could you clarify ? Knowing if it's from a specific website, a security system, or an old hard drive would help identify its exact origin. How to play MP4 files in Windows - Microsoft Support g371_001.mp4
If this was found in a downloads folder or a shared drive, it may simply be an automated filename from a screen recording tool or a video converter that hadn't been manually renamed. Many DVR and NVR systems (like those from