utopianism (n.)

1550s, with reference to More's fictional country; 1610s as "extravagantly ideal, impossibly visionary," from utopia + -an. As a noun meaning "visionary idealist" it is recorded by 1832 (also in this sense was utopiast, 1845). Utopian socialism is from 1849, originally pejorative, in reference to the Paris uprising of 1848; also a dismissive term in communist jargon, in reference to the ideas of Fourier, St. Simon, and Owen, "the pre-scientific and infantile stage" of modern, practical socialism.

word-forming element making nouns implying a practice, system, doctrine, etc., from French -isme or directly from Latin -isma, -ismus (source also of Italian, Spanish -ismo, Dutch, German -ismus), from Greek -ismos, noun ending signifying the practice or teaching of a thing, from the stem of verbs in -izein, a verb-forming element denoting the doing of the noun or adjective to which it is attached. For distinction of use, see -ity. The related Greek suffix -isma(t)- affects some forms.