1940s; earliest use found in The Times. From Spanish peronista, although this is first attested slightly later from the name of Juan Domingo Perón + -ista.
Definition of Peronista in US English:
Peronista
nounˌpɛrəˈnɪstə
Politics
Peronist.
adjectiveˌpɛrəˈnɪstə
Politics
Peronist.
Origin
1940s; earliest use found in The Times. From Spanish peronista, although this is first attested slightly later from the name of Juan Domingo Perón + -ista.