c. 1300, "courtesy, noble deeds," from kind (adj.) + -ness. Meanings "kind deeds; kind feelings; quality or habit of being kind" are from late 14c. Old English kyndnes meant "nation," also "produce, an increase."
"friendly, deliberately doing good to others," Middle English kinde, from Old English (ge)cynde "natural, native, innate," originally "with the feeling of relatives for each other," from Proto-Germanic *kundi- "natural, native," from *kunjam "family" (see kin), with collective or generalizing prefix *ga- and abstract suffix *-iz. The word rarely appeared in Old English without the prefix, but Old English also had it as a word-forming element -cund "born of, of a particular nature" (see kind (n.)). Sense development probably is from "with natural feelings," to "well-disposed" (c. 1300), "benign, compassionate, loving, full of tenderness" (c. 1300).
word-forming element denoting action, quality, or state, attached to an adjective or past participle to form an abstract noun, from Old English -nes(s), from Proto-Germanic *in-assu- (cognates: Old Saxon -nissi, Middle Dutch -nisse, Dutch -nis, Old High German -nissa, German -nis, Gothic -inassus), from *-in-, originally belonging to the noun stem, + *-assu-, abstract noun suffix, probably from the same root as Latin -tudo (see -tude).
c. 1300, "state or character of being unkind, lack of natural regard or proper consideration," from un- (1) "not" + kindness (n.), or from unkind (adj.) + -ness. Meaning "an unkind act" is from c. 1500.
<a href="https://www.etymonline.com/word/kindness">Etymology of kindness by etymonline</a>
Harper, D. (n.d.). Etymology of kindness. Online Etymology Dictionary. Retrieved $(datetime), from https://www.etymonline.com/word/kindness