It's from when arrays were just a block of memory and the index was the offset. So you'd start at pointer x and read memory from there. x + i was your memory location. So you'd start at x + 0 to read your first data element. x + 1 would be the location in memory of the second element.
The context is clear to a human. If an LLM is giving advice to everybody who asks a question in Google, it needs to do a much better job at giving responses.
It's hilarious that so many issues in Windows can be fixed with a restart but then they made it not actually restart when turned off and on again.