blood

Old English blod "blood," from Proto-Germanic *blodam "blood" (cf. Old Frisian blod, Old Saxon blôd, Old Norse bloð, Middle Dutch bloet, Dutch bloed, Old High German bluot, German Blut, Gothic bloþ), from PIE *bhlo-to-, perhaps meaning "to swell, gush, spurt," or "that which bursts out" (cf. Gothic bloþ "blood," bloma "flower"), in which case it would be from suffixed form of *bhle-, extended form of *bhel- (2) "to blow, inflate, swell" (see bole).

There seems to have been an avoidance in Germanic, perhaps from taboo, of other PIE words for "blood," such as *esen- (cf. poetic Greek ear, Old Latin aser, Sanskrit asrk, Hittite eshar); also *krew-, which seems to have had a sense of "blood outside the body, gore from a wound" (cf. Latin cruour "blood from a wound," Greek kreas "meat"), which came to mean simply "blood" in the Balto-Slavic group and some other languages.

Inheritance and relationship senses (also found in Latin sanguis, Greek haima) emerged in English by mid-13c. Meaning "person of one's family, race, kindred" is late 14c. As the seat of passions, it is recorded from c.1300. Slang meaning "hot spark, a man of fire" [Johnson] is from 1560s. Blood pressure attested from 1862. Blood money is from 1530s; originally money paid for causing the death of another.

Blood type is from 1928. That there were different types of human blood was discovered c.1900 during early experiments in transfusion. To get blood from a stone "do the impossible" is from 1660s. Expression blood is thicker than water attested by 1803, in reference to family ties of those separated by distance. New (or fresh) blood, in reference to members of an organization or group is from 1880.