This is the 4382nd most frequent Polish word.
historyk
"Historyk" means "historian" in English.
In this sentence, 'historyk' specifies a profession related to extensive historical studies.
Mój brat jest pasjonatem historii, ale nie jest zawodowym historykiem.
My brother is passionate about history, but he is not a professional historian.
This usage generalizes the role of a 'historyk' in academia or research.
Każdy historyk musi umieć pracować z różnymi źródłami informacji.
Every historian must be able to work with different sources of information.
Here, 'historyk' is used in its primary meaning as a professional who studies history.