What is the most innocent payment reference to indicate (and easy to explain to Bank if requested) when one private person from makes ~8k EUR one-time transfer to another person's bank account? Both parties are in Europe and using Banks/EMI.
Is anything being provided in return? If nothing is being provided in return, it sounds like a gift, in which case you could mark it as "gift". Check whether there are any gift taxes payable.
Honestly, I never got asked by any bank for mid-range 4 digit transfers.
For EMIs it might be different.
Maybe you could use 2 different sender and 2 different receiver accounts?
So every bank will just see a transfer of 4k EUR.
I don't believe there is anything you can write in that field that let the transfer go through if the bank or EMI has doubts on other parts say the sender.