What Rodin's Thinker is thinking?

• Sound that indicates "I wonder ..."
• Sound of deliberation
• 'Let me think ...'
• "You might just have a point ..."
• "Thinking ..."
• "That's odd ... "
• "Let's see ... "
• "Well, let me see …"
• Start of a response to a brainteaser

Douglas Harper's Etymology Dictionary Word definitions in Douglas Harper's Etymology Dictionary
representative of a sound made during contemplation or showing mild disapproval, attested from 1868, but this is probably a variation of the hum attested in similar senses from 1590s.