As most people know, Chess originated in India about 500 AD. Some of the pieces moved differently than the game have now.
Of all the pieces what underwent the most modifications was the one that sat next to the King.
It was originally known as the ferz. The name means “advisor to the king”. This definition is perhaps the most precise as the ferz sat next to the king at the start of a game. It was also was the weakest piece on the board; moving only one square diagonally (Kings don’t like to have powerful rivals sitting so close to them). But this lack of mobility also made the ferz much weaker than the king it was trying to protect.
Somewhere around 1000 A.D., chess made its way into Europe via Italy and Spain. Over the next 500 years the game spread throughout the next 500 years. However, the game went through a metamorphous during those years, especially in the last half of the 15th century.
Castling was introduced (but not fully accepted in its present form until the late 19th century), pawns could move forward two square on their first moves, and most of the other pieces gained mobility.
But the ferz went from the weakest piece to the strongest. Not only that, but it changed gender as well.
Several theories have been put forth how these two transformations came to be.
One is that as the pieces gained in strength, it was felt that the ferz needed to be upgraded as well to stay current. So extra powers were granted to the ferz that went well beyond any other piece. That may explain why the ferz became powerful, but not necessarily its change in gender.
Queen Isabella of Spain took the throne in 1474. She instituted many legal, economic, and political reforms. She is also the one who financed Christopher Columbus to find an alternate route to China (he failed of course).
By most accounts, she was a capable queen and more of a reformer and leader than King Ferdinand (her husband).
Chess was known in the kingdom of Ferdinand and Isabella.
In fact, Isabella learned chess along with her other studies while she was growing up.
There were, of course, many others who took up chess in a more serious fashion.
Lucena, the most famous Spanish player, or at least the most well known, at that time, wrote “Repeticion de amores e arte de axedrez con CL juegos de partido” in 1497. He dedicated his manuscript to King Ferdinand.
In his book he explicitly states the distinction between the old and new rules of chess, including rules about the new Queen (“de la dama”).
He didn’t present any new theories however. He got his information from Valencia which, then as now, is a part of Spain.
She, Queen Isabella, more than anyone else, was the inspiration for the new piece on the chessboard.