Interbase (the company, with a small 'b') started as Groton Database Systems in our spare bedroom in Groton, Mass. All the 'gds' tags and the 'g' prefix utilities (gfix, gpre, gbak) come from those days. The three founders had previously worked at DEC on the Rdb projects. We were (are) Jim Starkey who did the software architecture and wrote most of the code, Don DePalma who wrote documentation etc. and me, Ann Harrison. I brought in a salary and kept us from starving. That was 1984.
The system relations and the API were based on DEC's relational architecture, which would have been an excellent basis for a program to program relational database standard. It was extensible, supported SQL, QUEL, and DEC's own flavor of relational language. The design made multi-database programs quite simple and provided a good basis for distributed processing. Another ball dropped. Anyway, that's why the system relations are RDB$xxx.
In 1986, we (by now seven founders) sold stock to Ashton-Tate, a big company that would give us credibility and funding so we could get over the twin hurdles of 'Who are you guys?' and never having enough money to hire marketing talent to stir up leads to provide revenue to hire ...
Alas, Ashton-Tate decided that they really loved InterBase, so investing in database companies must be great, so they invested in Sybase too. [Bad day.] At that point, all they wanted from us was to be great, and to be just like dBase, and just like Sybase, and demonstrably faster than either of them at everything. Need I mention that that drained engineering resources?