Etymon
itc-merks-latin-merx-latin-mercor-protoindoeuropean-tus-protoitalic-tus-latin-tus-latin-mercatus-vulgar-latin-mercatantem-vulgar-latin-mercatantem-old-french-marcheant-old-french-ise-old-french-marcheandisebor
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.