'Ponder' is Latin for 'to weigh' — the mind as a balance scale, weighing thoughts like physical objects.
To think about something carefully and at length; to weigh mentally; to consider deliberately.
From Old French 'ponderer,' from Latin 'ponderare' (to weigh, to weigh in the mind, to reflect upon), from 'pondus' (weight, genitive 'ponderis'), which derives from 'pendere' (to weigh). The metaphor is exact: to ponder is to weigh thoughts as one weighs objects on a balance. The mind is conceived as a scale, and pondering is the act of placing ideas on it to judge their relative weight and merit. 'Pondus' also gives
The Statue of Liberty weighs about 225 tons. That is ponderous. But whether she is pondering anything is a matter of interpretation. Both 'ponderous' (physically heavy) and 'ponder' (to weigh mentally) come from Latin 'pondus' (weight). The physical and mental meanings have diverged so completely that English speakers never connect them — yet they are the same word applied