English has two vocabularies for almost everything: a Germanic one it was born with, and a Latin one it acquired after 1066 and kept acquiring for six hundred years. Where the same ancient root reached English down both roads, the inherited arrival ended up obscene and the borrowed one ended up learned. That is not a fact about the words. It is a fact about who was speaking which.

• Pick a word in the control bar. Each one gets its own sheet, because seven descents drawn together was unreadable and hid the thing that actually matters, which is what happened at each step.
• Every box gives three things: the form, the language it was in at that moment, and what it meant then. So you can see that *skei- meant "to cut, to split" before anything else happened to it, that Proto-Germanic narrowed it to what the body separates, and that Latin took the same root toward telling one thing from another, which is what knowing is.
• An asterisk means reconstructed. *skei-, *ḱel-, *ors- and *skītaną were never written down by anybody. They are inferred backwards from the attested forms beneath them, and the chart marks them so you can tell which rows are evidence and which are argument.
• Red is the line that ends somewhere you cannot print. Blue and green end in a dictionary. Solid means inherited or borrowed, dotted means the sense moved inside one language, and a line stopped by a bar is a connection that has been proposed and cannot be shown.
• Two of the seven have uncertain origins. The origin of fuck is uncertain. Piss is probably imitative; inherited in French and Italian, borrowed into English. A chart like this is only worth something if it admits where the trail stops.
• The taboo is younger than the words. Cunt named a street in Oxford around 1230 and appears in medical prose about 1400. It is avoided in speech from the fifteenth century and obscene only from the seventeenth, which is exactly the window in which the borrowed vocabulary arrived to do the same job in public.
• The words are printed in full. Asterisking them would make the page useless, since the entire subject is what these particular sequences of letters descend from.

Roots follow the standard references and each sheet cites them. Shit to *skei- is Etymonline's own analysis, which notes in the entry itself that the word "is thus a cousin to science and conscience". The deep etymology of Latin damnum is uncertain past Proto-Italic and the chart stops there rather than guessing.

Elsewhere: The Same Idea · The Missing N · Flat-Foot · Empty Orchestra · The Same Word · Signs for Sounds · Heartwood · Every Language Family