Best explanation I found was on Grammarist:
“Bound vs. bounded
The verb bind makes bound in the past tense and as a past participle. So, for example, if you tied together two things this morning, you bound them together, and the two things were then bound together. Bounded is the past tense and past participle of the verb bound, which has two main definitions: (1) to confine or serve as the boundary of, and (2) to leap or spring. For example, an island is bounded on all sides by water, and somewhere a rabbit bounded out of a bush this morning.”
I learned something today.

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