When the LARC arrived in Livermore in 1960 it was the first machine there with disk storage. Actually they were not disks but drums with moving heads. The opportunity arose to keep useful amounts of data on disk between machine shots. An important case was to store a production job and its data there to run while machine operators sought and mounted magnetic tapes for the next scheduled production run. This particular production job always had computing to do.
The LARC had no card reader so bringing a card deck to the machine for your debug shot was not an option. Those who could benefit from a small amount of space on the drums would wonder which drum addresses to use. There was an office with a blackboard where a list of such allocations were kept. If you staked a claim there, there was a good chance that no one else would write there. The machine had no operating system to enforce these rules.
I suppose that other institutions followed similar patterns and I presume that such was the origin of the earliest patterns a few years later of allocating disk space, only enforced by privileged code. The OS would have a notion of who was running and keep programs off other people’s space.