If this looks familiar, it's because I posted it somewhere else.
All refer to being readily accessible.
Accessible, Readily (Readily Accessible). Capable of being reached quickly for operation, renewal, or inspections, without requiring those to whom ready access is requisite to climb over or remove obstacles or to resort to portable ladders, chairs, etc.
I was reading the National Electrical Contractors Associations, book titled National Electrical Installation Standards, Good Workmanship in Electrical Contracting.
Commercial. panel boards shall be 6ft 7inch above the finish floor.
Residential. ADAG compliance, in dwellings the highest overcurrent device is a maximum of 48 inchs above the finished floor.
Makes you wonder, doesn't it.