The proper noun when spoken can be confused for the common noun.
“The Great Depression” as a proper noun only came into popular use in the 1950s, long after the event was over.
Frank is a proper noun of the masculine gender, in the singular number and third person.
If there is, then, whether the term is a common or a proper noun?
If a noun, he was certainly a very uncommon, but not strictly a proper noun.
Thus "John Smith" (particular; proper noun) and "Man" (general; common noun).
A proper noun often consists of a group of words, some of which are perhaps ordinarily used as other parts of speech.
A common noun becomes a proper noun when used as the particular name of a ship, a newspaper, an animal, etc.
The phrase would have been very familiar to the scribes from grammatical treatises ('proper noun').
A proper noun becomes a common noun when used as a name that may be applied to any one of a class of objects.