Extremism: what’s the cultural history of this word?

“Extremism” sounds like an ideology, by analogy with Marxism for example. Or it could be akin to a behavioural state like mutism or autism. With respect to these different directions, I’m wondering what the word’s political and cultural history is.

Lexico defines extremism as

The holding of extreme political or religious views; fanaticism.
‘Otherwise their anger and frustration can lead to religious extremism’

The word is a simple construct derived from the adjective extreme and seems unlikely to have a strong cultural development as opposed to filling a linguistic niche for a suitable related noun. According to Google ngram its use has increased steadily since the early 1900s.

Extremism = "the fact of someone having beliefs that most people think are unreasonable and unacceptable"

Cambridge dictionary

This meaning accords with other dictionaries and with common usage. The beliefs, which may be of any form (for examples: leftist/rightist, religious/atheistic, nationalist/globalist, communist/capitalist), are not innate but are chosen by the believers.

Because extremism is related to behaviour that is by definition outside that condoned by most people it is not akin to Marxism, which has a set of particular beliefs open to as many people as choose to embrace it.

Nor is it reasonably likened to mutism or autism, both of which are human conditions characteristic of some people but not in any sense chosen by them.