Aspen
late Middle English: from dialect asp (in the same sense) + -en2, forming an adjective later used as a noun (late 16th century).
wiktionary
From Middle English aspen, corresponding to asp + -en.
From Middle English aspen, from Old English æspen, Old English æspan(combining form), from Old English æspe(“aspen”). More at asp.
etymonline
aspen (n.)
European tree of the poplar family, late 14c., from adjectival or genitive form of Old English spe "aspen tree, white poplar," from Proto-Germanic *aspo, adjective aspin- (source also of Old Norse sp, 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").
