European tree of the poplar family, late 14c., from adjectival or genitive form of Old English æspe "aspen tree, white poplar," from Proto-Germanic *aspo, adjective aspin- (source also of Old Norse æsp, Middle Dutch espe, Old High German aspa, German Espe), from PIE *aps- "aspen" (source also of Lithuanian epu, Latvian apsa, Old Prussian abse, Russian osina), perhaps a northern European substratum word.
The current form in English probably arose from phrases such as aspen leaf, aspen bark (see -en (2)). Its leaves have been figurative of tremulousness and quaking at least since early 15c. (an Old English name for it was cwicbeam, literally "quick-tree").
updated on September 26, 2022