sentimentalism (n.)

1749, "pertaining to or characterized by sentiment, appealing to sentiment rather than reason," from sentiment + -al (1). At first without pejorative connotations; the meaning "too tender-hearted, apt to be swayed by sentiment" is attested by 1768 (implied in sentimentality). The French word is said to be from English. Related: Sentimentally.

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.

"quality of being sentimental," 1768, from sentimental + -ity. Compare sentimentalism.