Where does “intramyocardium” come from?

intramyocardium (English) comes from English intra-, from Latin intra, from Latin interus, from Proto-Indo-European h₁énteros, from Proto-Indo-European -teros — Contrastive or oppositional adjectival suffix.

Ancestry of “intramyocardium”, step by step

Step	Language	Word	Meaning
1	English	intra-	a prefix signifying inside, within, interior,...
2	Latin	intra	within; inside; during; less than
3	Latin	interus	—
4	Proto-Indo-European	h₁énteros	inside, within
5	Proto-Indo-European	-teros	Contrastive or oppositional adjectival suffix

Every word from Proto-Indo-European -teros →Every word from Proto-Indo-European h₁énteros →Every word from Latin interus →