Boringly, -inho is just a suffix that means little. So for example, Ronaldinho means little Ronald (His actual name is Ronaldo). So it's either a really boring name like Dave, or a really boring name like Dave with an -inho on the end haha.It seems like to be Brazilian you either have to have an amazing name with “inhio” at the end or a name like Dave, Malcolm or Alex! I hope Malcolm is better than Jo
If you're curious, I believe -ao is the opposite. So Luisao is big Lewis.
I haven't studied Portuguese in ages so apologies if I'm wrong.