Possible Clues:

• Exotic Parsee lady smiles briefly and I'm speechless!
• I'd keep mum's emeralds and paisley shift
• I'm no whistle-blower, physically incapable of leaking?
• "Your secret's safe with me"
• *"I won't tell a soul!"
• Secret assurance
• ''I'll never tell a soul''
• 'I'll never tell'
• ''No telling'' assurance
• Mum's the word