[sixdimensional]

In the world before centralized MDM systems which were independent of their other enterprise operational/transactional systems, some organizations treated the data in their core enterprise systems as "master files" (I'm talking about quite a while ago).

"The concept of master files was transferred to some corporate computers as early as the 1960s and gained popularity during the 1970s and 80s when computers became more abundant. Master files contain essentially the same descriptive data – such as names, addresses, and basic summary information – as master data. Master files continue to be used as a part of some system databases and were a precursor to master data." [1]

[1] https://www.dataversity.net/a-brief-history-of-master-data/