‘Cause, baby, now we got bad blood

You know it used to be mad love

So take a look what you’ve done.

‘Cause, baby, now we got bad blood

Just your good old Taylor Swift riddle about love and war, you may think. But think again when you look at the lyrics from a song of Bastille:

All this bad blood here, won’t you let it dry?
It’s been over for years, won’t you let it lie?

While reading these lyrics, the following question pops into your head: why are all those artists singing about “bad blood”?

“Bad blood” for “bad luck”

First of all, let’s look up the definition of “bad blood”. The free dictionary tells us that it is an expression used for a feeling of intense hatred or hostility. The word dates back to the 19th century, when the word was used as a term that referred to determined factors present in the blood of those with certain illnesses.

In other words, if you had “bad blood” you literally had bad blood (namely, containing a certain ill-natured factor), though the meaning differed highly. It could mean that the patient suffered from toxicity in the body, but it could also mean that the patient had a genetic predisposition to a disease.

Brothers out for blood

Enough about the medical history of the word. Let’s look at another development which can tell us more about the definition of the word.

I am talking about the so-called “blood feuds”. A blood feud, or “vendetta”, is a long-running fight between different camps, especially between social groups. These blood feuds usually arise from a feeling of being wronged and the seeking of avenging themselves for it. The principle “tit for tat” keeps the continuous cycle of revenge, involving a lot of violence, running.

These blood feuds find their origin in the Middle Ages, but even in modern times they are still practised in several areas, including France, Italy and England. Famous family feuds in the US were for example the Early-Hasley feud (an ideological battle over the same content as the American Civil War, which had taken place just before the feud) and the Hamilton-Burr feud (a political battle over the election of Aaron Burr as senator, while Alexander Hamilton had wanted to see Philip Schuyler as senator).

The war goes on

Back to today: how come the expression “bad blood” is still so frequently used, despite there being much less blood feuds and despite there being no connection whatsoever with the historical, medical definition of the word?

Well, although the definition of the word has changed throughout the years, the word hasn’t lost its historical content. The blood feuds might not be as violent and cruel as they once were, they are still brewing under the surface. Look at the conflict existing between Katy Perry and Taylor Swift (it is also this one conflict which her song refers to) over the fact that Katy would have “stolen” some of Taylor’s backup dancers before her Red tour began. Katy, on the other hand, claims that Taylor is the one who snatched away her dancers, as she had worked with these dancers before. Now the feud continues with Taylor writing songs about Katy and Katy letting her dancers wear red bikinis as a reminder of Taylor’s red tour.

As you can see, though the real “battles” might be over, the fights aren’t. To give expression to this hatred, people like to refer to a feeling of “bad blood”, something that might as well feel like an infection in the body system or a feud, just without all the blood.