Where does “Vishnuism” come from?

Vishnuism (English) comes from English ism, from English -ism, from Latin -ismus, from Ancient Greek -ισμός, from Ancient Greek -μός, from Proto-Indo-European -mós — Creates action/result nouns from verb stems.

Ancestry of “Vishnuism”, step by step

Vishnuism traces back through two separate lines of ancestry.

via English ism

StepLanguageWordMeaning
1EnglishismAn ideology, system of thought, or practice that...
2English-ismUsed to form nouns of action or process or result...
3Latin-ismus-ism
4Ancient Greek-ισμόςForms abstract nouns
5Ancient Greek-μόςForms abstract nouns
6Proto-Indo-European-mósCreates action/result nouns from verb stems

via English Vishnu

StepLanguageWordMeaning
1EnglishVishnuOne of the Trimurti (trinity) in Hindu mythology, and the most venerated god in Hinduism
2Sanskritविष्णुVishnu; name of the month चैत्र; name of the...
3Sanskritविषpoison, venom, bane; poisonous; servant,...
4Proto-Indo-Aryanwiṣás
5Proto-Indo-Iranianwišáspoison, venom
6Proto-Indo-Europeanwisósfluidity, slime, poison; poison; poison; slime;...
Every word from Proto-Indo-European -mósEvery word from English -ismEvery word from English ism