The i version started from 8i onwards. It stands for oracle internet.
Because till then (in version 8)it did not support data transfer over the internet.Actually in those time internet was hardly used. This was supported in 8i.
Next was 9i with some of the enhanced features of 8i
Next was 10g, it stands for Oracle GRID,because it supports grid architecture.
next in database is 11g
As i said 11i is not database its ERP.