Validation name must begin with a letter

What causes this issue?

The name of the validation must begin with a letter (and not with a
number). You can use the following letters:
ABCDEFGHIJKLMNOPQRSTUVWXYZ

System Response

The system issues an error message and will not allow you to continue with this transaction until the error is resolved.

How to fix this error?

Re-enter the name of the validation.

Error message extract from SAP system. Copyright SAP SE.