خَفِيَ: اِخْتَفَى to disappear, banish; to hide (oneself), conceal oneself; to be hidden, obscured, concealed; to be unknown; to remain (a) secret

لاَ يَخْفَى (أَنَّ) it is well known (that); it is obvious (that), it is clear (that), it goes without saying (that)