c. 1500, "characteristic of one who is submissive or obedient," from Late Latin subiectivus "of the subject, subjective," from subiectus "lying under, below, near bordering on," figuratively "subjected, subdued"(see subject (n.)). In early Modern English as "existing, real;" more restricted meaning "existing in the mind" (the mind as "the thinking subject") is from 1707, popularized by Kant and his contemporaries; thus, in art and literature, "personal, idiosyncratic" (1767). Related: Subjectively; subjectiveness.
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/subjectivism">Etymology of subjectivism by etymonline</a>
Harper, D. (n.d.). Etymology of subjectivism. Online Etymology Dictionary. Retrieved $(datetime), from https://www.etymonline.com/word/subjectivism