Definitions for "-nik"
A suffix attached to other words indicating a person with certain characteristics or associated with a certain group or behavior; as, beatnik, kibbutznik; it is sometimes used derogatorily; as in no-goodnik, peacenik.
The English suffix -nik is of Slavic origin. It approximately corresponds to the suffix "-er" and nearly always denotes an agent noun (that is, it describes a person related to the thing, state, habit, or action described by the word to which the suffix is attached). In the cases where a native English language coinage is possible, the "-nik"-word often bears an ironic connotation.