Etymon
pie-oktow-protogermanic-ahtou-protoindoeuropean-dekm-protogermanic-tehun-protogermanic-ahtoutehun-anglian-old-english-eahtatene-middle-english-eightetene-english-eighteen-pregreekder
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.