This mapped very awkwardly to digital subscribers who we had individual data on. We were able to join databases in a way that sort of works through more or less (mostly less) comfortable assumptions. The queries are not pretty.
Hilariously, it has dozens of names, because it just comes up in so many places for so many people. It appears that "record linkage" is the term that has won the top spot at Wikipedia: https://en.wikipedia.org/wiki/Record_linkage
Record linkage seems to be concerned with joins that aren't guaranteed to be correct because there are no unique keys.