The phrase "a man of unknown" is not correct in written English as it is incomplete and lacks a noun to clarify what is unknown.
It could be used in contexts where you want to describe a man whose identity or background is not known, but it needs to be completed for clarity.
Example: "He was a man of unknown origins, and no one knew where he came from."
Alternatives: "a man of mystery" or "a man of uncertain background".
Another, dubbed "Suspect #1" in an imgur post called 4chan ThinkTank, is a man of unknown ethnicity with dark skin and short, nearly buzzed black hair, wearing tan cargo pants and a black jacket.
Jan Długosz described John Hunyadi as "a man of unknown origin", and he is likewise mentioned as "a Vlach by birth, not highly born" by Aeneas Silvius Piccolomini.
Summer was married to a man of unknown employment, who occasionally swung by the back entrance of the shop wearing a hoodie and dark sunglasses, driving a gold Mercedes SL.
A 33-year-old man of unknown serological HIV status died before discharge from hospital, from respiratory problems of a less sudden nature than the 2 others.
The man, of unknown nationality, was displayed today sitting in the same car, guarded by two security guards.
For some reason, this young, smiling, slightly aloof but hardly intimidating man of unknown ethnic origin (my parents dared not ask) held sway over many of the residents.
Rabbi Yitzhak Kaduri, the holy man of unknown but tremendous age, was scheduled to visit the Hall of Moses synagogue and then a candlelit graveyard in this Tel Aviv suburb tonight for a rally that mixed mystic ritual with all the grit of Chicago ward politics.
Today Mr. Sprecher, a man virtually unknown outside of financial circles, is poised to buy the New York Stock Exchange.
It might seem remarkable that someone like Mr. Weinstein, a man virtually unknown outside of financial circles, could deal such a stinging blow to one of the world's largest, most respected banks.
Mr. Goodwin, a man previously unknown to most of the Senate, is slated to remain in office only until he is replaced in November, not allowing him much time to get familiar with his new co-workers.
United Nations peacekeepers operated checkpoints alongside Sierra Leone soldiers, militiamen and rifle-toting men of unknown affiliation who were dressed mostly in T-shirts and flip-flops.
