Ironically ‘curry powder‘ isn’t something you will likely find in India, though that is the cuisine with which it is most often associated. There are also Chinese, Japanese, Southeast Asian, and North African versions. In fact curry is more a style of cooking ( it literally translates to gravy or sauce ), adding the herbs individually, but commonly combined with others.
And an even greater irony - ‘Curry Plant’ (Trigonella foenum-graecum) which is often used in Indian cooking is not an ingredient in curry powder. ( It is actually the leaf of the fenugreek plant - called Methi in Indian cookbooks ).
It’s all so complicated… the seed of the fenugreek plant, which we know as fenugreek - is an ingredient in the recipe for curry powder. It is likely that the blend was developed by the British when India was part of the empire, and returned home to make it easier to replicate the cuisine.
Many of the herbs (turmeric, ginger, peppers) are being studied for their potential medicinal benefits.