Meaning of UNKNOWN in English
DUBIOUS : I don't like driving on unknown roads.
GOOD : I don't like driving on unfamiliar roads.
DUBIOUS : The names on the list were unknown to me.
GOOD : The names on the list were unfamiliar to me.
unknown usually describes something that people in general do not know or know very little about: 'Whether or not there is life on any of these planets remains unknown.' 'There are still some unknown species of animals in the South American rain forests.'
Something that you yourself have not seen, heard or experienced before is unfamiliar ( to you): 'The voice on the phone sounded unfamiliar.' 'It took Steven some time to get used to his unfamiliar surroundings.'
Longman Common Errors English vocabulary. Английский словарь распространенных ошибок Longman. 2012