こっそり の訳語→ creep discreetly furtively privately quietly sott-voce stealthily unperceived unseen
それとなく の訳語→ absently carelessly casual casually cautiously covertly cunningly delicately discreet friendly generally gently little obliquely somehow subtly unobtrusively vague veiled
ひそかに の訳語→ mentally private secretly silently softly unadvertised