*aspō

From a northern Eurasian tree-name *aps- ~ *ops- of uncertain origin, often treated as an old Wanderwort or substrate word rather than as a securely inherited Proto-Indo-European lexeme. Proto-Germanic *-sp- apparently reflects metathesis of *-ps-, perhaps encouraged by *askaz. Compare Latvian apse, Old Prussian abse, Lithuanian ãpušė and ẽpušė, and Proto-Slavic *opsā and *ōpsīkā, all denoting the aspen. Finnish haapa and comparable Turkic forms support a wider Eurasian Wanderwort, but neither its ultimate source nor the direction of borrowing can be established with certainty (Derksen 2008: 378, s.vv. *osa; *osìna; *esìka; Jakob 2024: 219, 278, 289 n. 10; Kroonen 2013: 39; Matasović 2024: 58; Šorgo 2020: 434). Witczak (1991: 65–75) makes a compelling argument that Old Armenian ոփի (opʻi) comes from PIE *ops- (it cannot be derived from the alternative *aps-). Mallory and Adams (1997: 33) make a case for the word being Indo-European if the Armenian and Old Indic forms indeed come from the same root, since this would prove that it is more widespread than just northern Europe. Nevertheless, this cannot disprove the possibility of an early, widespread Wanderwort.