Why is the name 'APPS' given to Oracle Technologies?

Let's assume that you are working on Inventory and Purchasing Modules. You want to create Tables, Indexes, Sequences, Synonyms,package scripts etc......You can create everything in your custom schema i--e, XXXINVor XXXPO. But the recommended process is to create Tables, Indexes,Sequences in your custom schema i--e, XXXINV or XXXPO and create the synonyms of the same in APPS schema. and creating other scripts like package scripts in APPS schema .

The reason why you create Tables,Indexes,Sequences etc.. in Custom schema and package scripts in APPS schema is :::::: It's simple. Having all the scripts belonging to different modules in one schema. At the time of migration other than tables everything can be taken from this central schema (APPS) and can be migrated accordingly.
The tables are still owned by their respective schema, but now we have a central schema named APPS. Oracle ERP simply connects to APPS database schema for all its operations.

For Example: Your Project is having modules like INV,PO,PA,GL,AR,AP,QA etc.. then you have to maintain your database in such a way that all the tables and their related scripts are defined in their respective custom schemas and the synonym for the same is defined in APPS schema. Before creating the synonym, you need to give all GRANT permissions to the APPS schema from your custom schema. And create all the package scripts of INV,PO,PA,GL,ARA,AP,QA etc.. in APPS schema. So that at the time of migration it becomes easier to migrate all the stuff from one CENTAL schema............i..e, APPS.

So the name APPS for Oracle Technologies.