Where does “cephalodynia” come from?

cephalodynia (English) comes from English -odynia, from Ancient Greek ὀδύνη, from Proto-Indo-European h₁ed- — to eat.

Ancestry of “cephalodynia”, step by step

Step	Language	Word	Meaning
1	English	-odynia	pain
2	Ancient Greek	ὀδύνη	pain of body; pain of mind, grief, distress
3	Proto-Indo-European	h₁ed-	to eat