This is the 12790th most frequent Polish word.
nieznanej
"Nieznanej" means "unknown" (feminine form in Polish).
In this sentence, 'nieznanej' is used as an adjective describing 'nationality,' illustrating lack of knowledge or familiarity.
Spotkałem się z osobą nieznanej mi narodowości.
I met a person of a nationality unknown to me.
Here, 'nieznanej' is an adjective referring to the 'era,' conveying that the specific time period is unidentified.
Książka z nieznanej epoki została odkryta.
A book from an unknown era was discovered.
In this example, 'nieznanej' is used as an adjective modifying 'origin,' indicating an unrecognized or mysterious aspect.