Etymon
enm-ficcioun-english-fiction-protoindoeuropean-ke-protoindoeuropean-kom-protoitalic-kom-protoitalic-kom-late-latin-con-protoitalic-merks-late-latin-merx-protoindoeuropean-yos-protoitalic-ios-old-latin-ios-latin-ius-late-latin-ium-late-latin-commercium-protoindoeuropean-h2elder
A dedicated page for this root is on the way — it will gather every word descended from it, sibling forms across daughter languages, and a branching map of the family tree.