Ask HN: How do you name subsystems in your org

I work for a growing org where we are starting to have various in house applications that are separated into apis/sub systems that either produce or consume data e.g. HR attendance, Visitor Management, Warehousing e.t.c Our Parent company have a method where they name their systems using the planetary system e.g Sun is their huge SQL cluster where they store most of their data, Earth is their operational application for ops. I hope you get the picture. What other naming conventions have you guys comes across?