oi provides location-annotated io::Errors so you can display useful error messages to your users.
Error messages without location information are often not actionable, especially when they come from a complex program with many potential sources of errors.
Compare an unannotated error:
sh
$ foo
No such file or directory (os error 2)
…with an annotated error:
sh
$ foo
Configuration.toml: No such file or directory (os error 2)
Aside from being "io" backwards, oi is also an exclamation, as in Oi! Oi! Oi!. Imagine alerting your users to the location of errors: "Oi! 1.2.3.4 is unreachable!"