The name of the column should denote that it is a natural (business) key. I Haven't found any recommendations or good practices for this naming (e.g. columnName_NK, NKey_columnName, columnName_ID)?
My preference is to use BK at the end of the column name.
BK is not a very common combination in English language words, even less so at the end of the word. This makes it easy to programmatically identify your business keys.
It is easily understood without additional documentation.
Adding it at the end allows the eyes to easily read the definition of the column (PersonBK vs BKPerson)