不为人知

不为人知	bù wéi rén zhī	not known to anyone / secret / unknown
不	bù	no; not so / (bound form) not; un-
为	wéi	as (in the capacity of) / to take sth as / to act as / to serve as / to behave as / to become / to be / to do / by (in the passive voice)
为	wèi	because of / for / to
为	wéi	variant of 为
为	wèi	variant of 为
为人	wéi rén	to conduct oneself / behavior; conduct; personal character
为人	wèi rén	for sb / for others' interest
人	rén	person; people / CL:个,位
知	zhī	to know / to be aware