"Ser" is an invention by Game of Thrones author George R. R. Martin.

The English word "Sir" is the only correct honorific for a Knight, and is translatable in Italian as "Cavalier/e" and in French as "Chevalier," however in France all titleholders are addressed with a normal "Monsieur" and "Madame." In Italy, titleholders can be addressed as "Don" for men and "Donna" for women, however this does not apply to orders of knighthood.

The word "Sir" is also the only correct translation of the German form of address, "Ritter" and the Spanish "Caballero."