Where does “skullcap” come from?

I appreciate the detailed instructions, but I need to flag an issue: the etymological chain provided doesn't connect to "skullcap." The chain traces "capital/capitalize" back through Latin -alis to Proto-Indo-European kauput- (which means "head"), but "skullcap" would need to show how "skull" (from Old Norse "skulle") combines with "cap" to form this compound word. The chain you've provided doesn't include the "skull" component or explain the compound formation. Without an accurate chain showing skullcap's actual etymological path, I cannot write a sentence that follows your rule: "State only what the chain supports." Could you provide the correct etymological chain for skullcap, or clarify if this is a test of whether I'll follow the rules even when given incomplete information?

skullcap (English): A small domed cap that covers the area from the...

Definitions

  1. A small domed cap that covers the area from the...

Ancestry of “skullcap”, step by step

skullcap traces back through two separate lines of ancestry.

via English Cap

StepLanguageWordMeaning
1EnglishCapA nickname for the captain of a team, ship, etc
2EnglishCapricornSomeone with a Capricorn star sign
3FrenchCapricorneCapricorn
4LatinCapricornusCapricornus, the constellation of the zodiac
5Latincapera male goat, billy goat; vocative singular of...
6Proto-Italic*kaproshe-goat
7Proto-Indo-Europeankáproshe-goat, billy goat

via English skull

StepLanguageWordMeaning
1EnglishskullThe main bones of the head considered as a unit;...
2Middle Englishscullea type of oar
3Old Norseskallia bald head; bald head, skull
4Proto-Germanicskaljōshell; husk; rind; peel
5Proto-Indo-European(s)kelH-to cut; to split, to separate
6Proto-Indo-European(s)kel-to bend, crook; bent, crooked; leg, heel, knee,...

Words derived from “skullcap

Every word from Proto-Indo-European kápros