ذلك المعنى متعينا مشخصا أو لم يكن، والأول يسمى علما
The single meaning may designate a determinate individual or may not; the first case is called a proper name.
When “Zayd” designates one specified person, it functions as an ʿalam (proper name) and relates to the category of genuine particulars.
Many distinct people can happen to share the name Zayd. That does not make the meaning intended in a particular use universally predicable of all of them. Repetition of a name across people is different from the predicability of one common concept.