A Burden Off the Mind: A Study Guide on the Five Aggregates is Compiled by Thanissaro Bhikkhu. The khandhas which are commonly rendered as “aggregates” in English were one of the most important new concepts in the Buddha’s teaching. The Pali term khandha had very everyday meanings before the Buddha: A khandha is a bulk, a pile, a bundle, or a heap.
It could also be a tree’s trunk. The Buddha, on the other hand, gave it a new, psychological meaning in his first speech, coining the phrase “clinging-khandhas” to sum up his interpretation of the truth of stress and suffering. He alluded to these psychological khandhas again for the rest of his teaching career.
Since then, every generation of Buddhists has recognized their significance in his teachings.