heart-blood
/ˈhɑːtblʌd/noun
1Blood from the heart; blood shed in death; vital blood. More generally: blood.
2 Figurative. Something that gives energy or vitality to a place, institution, enterprise, etc.; a driving force.
Origin
Middle English; earliest use found in Ancrene Riwle. From heart + blood. Probably originally reflecting a genitive compound with unmarked first element.