Etymon
en-serum-english-sero-protoindoeuropean-ke-protoindoeuropean-kom-protoitalic-kom-old-latin-com-late-latin-cum-protoindoeuropean-kerd-protoindoeuropean-ker-protoindoeuropean-krd-protoitalic-kord-late-latin-cor-late-latin-concors-protoindoeuropean-h2-protoindoeuropean-eh2-protoindoeuropean-yeti-protoindoeuropean-eh2yeti-protoitalic-ao-late-latin-o-late-latin-concordo-late-latin-concordantiader
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.