“Blood and thunder” is an oath and a phrase. It is used as a curse and as an expression of surprise. While not necessarily religious in origin, it was used to avoid saying God’s name as a swear word. This kind of avoidance is called a ‘minced oath.’ The saying led to a spoonerism in America called “thud and blunder,” an article title about mistakes.
The phrase turns up in a number of literary works including poems, novels and plays. Lord Byron’s poem “Don Juan” has a line that runs as follows: ‘Oh blood and thunder! And oh blood and wounds! These are but vulgar oaths.’ Tobias Smollet’s 1751 book “The Adventures of Peregrine Pickle” also contains the phrase. Such was its usage during the 19th century that it spawned a series of blood and thunder penny dreadfuls, or dime-a-dozen romances.
Minced oaths are a type of euphemism. One or several words are removed and replaced with less repugnant alternatives. These alternatives are often related in form or sound to the original. In this way, ‘God dammit’ becomes ‘Gordon Bennett.’ Such phrases are non-literal idioms and are widely understood within their language or culture, but are difficult for new language learners to get to grips with.
The blood of “blood and thunder” may be linked back to an older swear word: ‘bloody.’ Still used in Britain as a means of exaggerating an adjective, its origin is disputed. Some believe it to be a contraction of ‘by our lady,’ meaning the Virgin Mary. Others believe it to be from the reign of Queen Mary of England, who was known as ‘bloody Mary’ because of her anti-Protestant purges.
In 1914, George Bernard Shaw included the word in his play “Pygmalion.” In it, one character exclaims ‘Walk! Not bloody likely!’ The exclamation caused a stir in those more restrained times. This is because "bloody" started out as an innocuous term, but gained a ruder meaning in the late 1700s.
“Blood and thunder” may be a modern minced oath, but it could relate to an old pre-Christian oath. Thunder is represented as an elemental deity in a number of religions. This includes Anglo-Nordic paganism. The word thunder itself comes from Thunor, the English rendition of Thor. With blood oaths and blood sacrifices, “blood and thunder” may have originated from a blood oath to the thunder God.
As well as appearing as a line or phrase in a number of literary works, “blood and thunder” has also been used as a title for other forms of popular culture. In the 1990s, the Norwegian musician Mortiis released a two-track EP of the same name. The phrase also featured as a song title on the 2004 concept album ‘Leviathan’ by band Mastodon. It was also used as the title of a short-lived comic book series released by Games Workshop and was set in the Warhammer 40,000 universe.