Blood in Proto-Indo-European
PIE distinguished two roots for "blood", depending on whether it was found inside the body or outside. The former was *h₁ésh₂r̥, the latter *krewh₂-. The lexical distinction between the two is argued to indicate two distinct metaphorical sets, which have been preserved in various derivatives and extensions in the daughters.
The root *krewh₂- yielded words signifying aggression (e.g. in derivatives such as Latin crūdēlis (“cruel”), Sanskrit क्रूर (krūra, “cruel”) and Ancient Greek κρούω (kroúō, “to beat, whip, crush”)) and dying, seen metaphorically in terms for the hardening (or freezing) of "outside blood" (e.g. in derivatives such as Latin crusta (“crust”), Old Irish crúaid (“hard”), Latvian kreve (“coagulated blood”) and Ancient Greek κρύος (krúos, “cold”)). The semantic field was thus associated with wounding, death, and drying out/hardening of the body.
On the other hand, the root *h₁ésh₂r̥ has been associated with the notion of life-giving bodily fluid, and also with the patrilineal line in kinship terminology.
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