In everyday English, blood is the red fluid that moves through veins and arteries, carrying oxygen and nutrients. The same noun also names kinship, temper, and violence: blood relatives, hot blood, a thirst for blood. Those extensions are old. The noun itself is older still, and it is native English, not a medieval import.
What is settled about the origin of the word blood is the Germanic chapter. The last step, into a reconstructed Indo-European root, is not.
Inherited, not borrowed
English did not take this word from Latin sanguis or French sang. It comes down in a straight line from Old English blōd, already the ordinary name for the circulating fluid before the Norman Conquest. The earliest known use falls in the Old English period, before 1150. Middle English kept the spelling blood, and modern English still writes it that way even though the vowel later shortened.
Behind Old English stands Proto-West Germanic *blōd and, further back, Proto-Germanic *blōþą. That ancestor yields a tight family of cognates: German Blut, Dutch bloed, West Frisian bloed, Old Norse and modern Icelandic blóð, Danish, Swedish and Norwegian blod, and Gothic blōþ. Scots blude and bluid sit beside English as close kin, not as loans. Across this set the core meaning stays remarkably stable: the bodily fluid.
A root that will not sit still
Beyond Germanic the trail fades. There is no undisputed match in Latin, Greek, or Sanskrit for this particular noun. That gap has produced several proposals, none of them settled.
One long-standing account links Proto-Germanic *blōþą to a Proto-Indo-European formation built on a root meaning to swell, bloom, or burst out, sometimes reconstructed with a -to suffix. On that reading the word would have named what gushes or spurts. Some scholars connect the same root to the Germanic verb for blooming, so that blood would sit near flower in the family tree, perhaps by way of a flushed or blooming red. The American Heritage Dictionary still points readers to that thrive-and-bloom root. Guus Kroonen has also suggested a tie to the Germanic verb meaning to blow, with a picture of liquid forced outward. Eric Hamp accepted a participial sense, gushed or spurted, after a head noun dropped away.
Dirk Boutkan, working from a stricter view of what counts as a secure Indo-European etymology, finds none and treats the word as likely non-Indo-European. Joseph Pentangelo has argued that the initial b shared by blood, bone, beard, breast, and bosom is a Germanic sound-meaning pattern, and that blood may have been reshaped from an older word for something that flows, the ancestor of flood.
What these accounts share is uncertainty. English blood is securely Germanic. Its last step into a reconstructed Indo-European root remains a matter of debate.
Why Germanic may have needed a new name
Indo-European languages already had older words for blood. One family, reconstructed around *esen-, appears in Sanskrit asṛk, Hittite ēshar, Old Latin aser, and a poetic Greek form. Another, *krew-, seems to have meant gore or blood outside the body; Latin cruor belongs here, while Balto-Slavic languages later used related forms as the ordinary word for blood itself.
Germanic largely set those inherited terms aside. Etymologists often explain the replacement as taboo avoidance: a culture that treated blood as ritually charged might drop the old name and reach for a newer, perhaps more descriptive, label. Proto-Germanic also had another word, *dreuzaz, for blood or gore, which did not become the main English noun. If *blōþą began as a euphemism or a vivid substitute, that would fit the pattern, though it remains a hypothesis rather than a documented event.
English blood itself has no living prefix or suffix. If the old -to analysis is right, the morphology belongs to prehistory, not to the word speakers use now. Later formations such as bloody and the verb to blood are built on the noun, not the other way around.
From fluid to family, temper, and slang
The bodily sense is the oldest in English and never left. Figurative uses grew around the idea that blood was the stuff of life and the seat of feeling.
By the mid-thirteenth century the word could mark inheritance and relatedness, a development that also appears independently in Latin sanguis and Greek haima. By the late fourteenth century it could mean a person of one’s family or kindred, or an offspring who inherits another’s blood. Around 1300 it already named temperament and natural disposition. Bloodshed as a stand-in for killing is an old extension as well. Medieval physiology treated blood as one of the four humours, associated with warmth and cheerfulness, which helped the temperament senses take hold.
Later English added social color. From the sixteenth century, a blood could be a fiery young man, a rake or a dandy. As a verb, from the 1590s, to blood meant to stain with blood or to make someone bleed; a hunting sense, giving an animal its first taste of blood, is later still. Technical compounds are more modern: blood money in the sixteenth century, originally payment for causing a death; blood pressure in the nineteenth; blood type in the twentieth, after transfusion experiments showed that human blood is not all one kind.
The saying that blood is thicker than water, used of family ties across distance, is attested from the early nineteenth century. To get blood from a stone, for an impossible extraction, is older, from the seventeenth.
A spelling that outran the sound
The spelling blood still looks as if it should rhyme with food. In most modern accents it does not. Old English had a long vowel. After the Middle English period that vowel shortened in a small set of words, and blood joined flood in taking the short central vowel of southern British and General American English. Some northern English and Irish varieties keep a shorter rounded vowel. The written form froze earlier than the pronunciation.
The cognates, not the guesswork
If you want one solid fact to keep, keep the Germanic set rather than any single Indo-European reconstruction. A speaker of German, Dutch, or Icelandic is using a sister of English blood, not a translation borrowed from elsewhere. The word has been in English since the language’s earliest records. The live puzzle is not how it entered English, but why Germanic speakers, unlike speakers of Latin or Sanskrit, stopped using the older Indo-European names for the same fluid.