The term scrutineering isn't F1 specific jargon but largely used in most forms of motorsport where the vehicle/bike is inspected to ensure it complies to a set standard.

For example in another sport motocross, dirt bikes need to pass scrutineering to ensure the bikes are within specification. This often includes checking the riders gear to ensure it is safe.

In American motorsports such as NASCAR, the term "tech inspection" is used for those stuff.

The term 'scrutineering' arguably extends beyond adherence to technical specifications to include procedural regulations within the sport. I'm not sure if this also applies to 'tech inspection' in e.g. NASCAR.

I've only heard it used in elections before. Each candidate will nominate scrutineers to ensure the count is valid.