1824, "the policy of opposition;" see negative (adj.) + -ism. Or, specifically, "the views of a negationist" (one who simply denies beliefs commonly held without asserting an opposite view). Related: Negativistic.
c. 1400, negatif, "expressing denial" (a sense now rare or obsolete), from Anglo-French negatif (early 14c.), Old French negatif (13c.) and directly from Latin negativus "that which denies," from negat-, past-participle stem of negare "deny, say no" (see deny).
The meaning "expressing negation" is from c. 1500; that of "characterized by absence of that which is affirmative or positive" is from 1560s. Algebraic sense, denoting quantities which are a subtraction from zero, is from 1670s. The electricity sense is from 1755.
Negative Capability, that is when a man is capable of being in uncertainties, Mysteries, doubts without any irritable reaching after fact and reason. [John Keats, letter, Dec. 21, 1817]
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.
<a href="https://www.etymonline.com/word/negativism">Etymology of negativism by etymonline</a>
Harper, D. (n.d.). Etymology of negativism. Online Etymology Dictionary. Retrieved $(datetime), from https://www.etymonline.com/word/negativism