Interestingly, this Proto-Germanic word is thought to be related to the Latin "asculus", which refers to the oak tree. This connection suggests that the ancient Germanic peoples may have originally used the term "aspa" to refer to a tree with similar characteristics to the oak, before it eventually became specifically associated with the aspen.
While the exact meaning of "aspa" is unknown, it is likely that the word was chosen because of the tree's trembling leaves which, according to some theories, were seen as a symbol of trembling or fear.
The word "aspen" has retained its Germanic origins, and its meaning has remained relatively consistent over time. It is now used to refer to the poplar tree that is known for its trembling leaves.