There are a fair number of curious idiosyncrasies within the systems of royalty and aristocracy, but perhaps one of the most popular queries relates to the well-known phrase ‘a person of blue-blood’. 

But what does this curious phrase actually mean? 

What Does Blue Blood Mean? 

In modern parlance, to say a person has ‘blue blood’ is to suggest that they come from a refined heritage such as royalty or the aristocracy. 

The term has come to mean that a person with blue blood has a noble lineage, it’s an observation of their bloodline, i.e. that they were born into a good, respectable, traditional or aristocratic family. 

In today’s usage, the term blue blood is rarely a direct observation of the person’s blood colour, but rather a symbolic reference to the family they were born into. 

Though it’s not a new phrase – having been recorded for a number of centuries – the connotations of this curious idiom have broadened over time. 

In times past, the term ‘blue blood’ may have been more of a distinct definition that related to royal birth. For example, to say that a person had blue blood would indicate that they belonged to a royal family line. 

Over the centuries, however, the phrase has come to include a wider range of noble lineage. These days it is used to suggest not only royal bloodlines but also includes aristocratic lineages, or even just a respected and established family line. 

So, in essence, the term ‘blue blood’ indicates a royal, noble or esteemed pedigree. It’s a colloquial term to mean good breeding. It’s not so much a reference to any physical characteristics or biological conditions, but rather it’s used to suggest an individual’s family line and heritage. 

Where Did The Phrase ‘Blue Blood’ Originate? 

The origins of such a curious phrase has sparked much debate over the centuries, with some outlandish suggestions being put forward as to why a person’s blood may be blue, rather than the red hue associated with normal blood colour. 

While the term ‘blue blood’ has come to be symbolic rather than literal, it’s likely that the origins of this phrase did relate to the idea of certain physical characteristics. 

Here are some of the suggested origins for the term ‘blue blood’. 

The Spanish Legend Of Sangre Azul

There is a theory that the modern phrase ‘blue blood’ originated with the Spanish phrase sangre azul (which translates literally as blue blood). 

This idea relates to the ancient families of the Castile region of Spain, who liked to clarify the pureness of their bloodline, i.e. that it was solely the product of the esteemed Castille families and pedigree, and not interrelated with any of the opposing or surrounding nations of the period. 

Map showing the Kingdom of Castile in 1210 – Alexandre Vigo, CC BY-SA 3.0, via Wikimedia Commons

There is speculation that these noble Castile families were of fairer skin, which would naturally reveal more of the blue veins beneath. This gives rise to the idea that these noble Castilian families could be identified by their fair skin and the blueish tint from their highly visible veins, i.e. their ‘blue blood’. 

Pale Skin & Blue Veins

This idea of pale skin and visible veins is a popular explanation for the use of the term blue blood. For many, it extends beyond the select Spanish families of ancient Castile, and applies to any kind of noble or aristocrat. 

The suggestion is that a life of leisure, in warm, decadent surroundings, is conducive to thin, pale white skin, i.e. the kind of skin that makes the blue veins beneath more visible, giving it a bluish hue.

The pale skin of those who enjoyed lavish noble lifestyles was in contrast to the weathered, sun-tanned skin of the working classes of the Middle Ages, who would spend large periods outdoors. During this period, any kind of sun-bronzed skin was an indication of farm labour or outdoor work. 

As a result, it was very fashionable for the noble classes to hide from the sun. This is why so many noble ladies would always take a parasol on their walks around the estate grounds or their trips into town, and why aristocratic carriages would be covered to shield their noble passengers from the weather. 

The contrast of noble lifestyles in comparison to the rural toils of the peasant folk was evident in the different types of skin. This explains why the blue blood (i.e. pale skin) reference is such a clear visual indication of the type of family or heritage a person comes from.  

Copper or Silver In The Blood

In medical terms, it’s believed that excess copper in the blood can cause the blood to turn blue. Given that regional diets may have included varying degrees of certain minerals, it’s possible that some remote lineages could have been characterised by blood that was bluer than the norm. If these family lines were related to a degree of nobility or esteemed heritage, it’s possible that the term ‘blue blood’ could have been a literal reference to their unusual blood colour. 

Another theory is that ingesting silver can cause discolouration of the blood. It’s easy to imagine that the royals and aristocrats of the ages would have been more likely to ingest silver – whether accidentally or in trace amounts from their wine goblets or banqueting dishes, for example – than the ordinary people who would have had far less access to any kind of silver objects. 

So perhaps the term ‘blue blood’ did originate as a literal description of the bluish tint to the blood of the royals and aristocrats, possibly as a result of the prevalence of silver in their luxurious lifestyles. 

In literal terms, to be a person of blue blood is a sheer accident of birth – it simply means being born into a family of pedigree. 

It’s one of the characteristics that have defined the evolution of aristocracy over the centuries, the idea that a person’s lineage and heritage is a defining factor in their role in society. 

While times have changed and modern cultures allow for much more social mobility and fluidity, the idea of blue blood origins is reminiscent of times past, when the details of a person’s bloodline could make or break their destiny.