also kiddie; 1570s as "young goat;" 1780 as "flash thief;" 1889 as "little child," from various senses of kid (n.) + -y (3). Other diminutives in the "small child" sense were kidlet (1889), kidling (1899). Related: Kiddies.
c. 1200, "the young of a goat," from a Scandinavian source such as Old Norse kið "young goat," from Proto-Germanic *kidjom (source also of Old High German kizzi, German kitze, Danish and Swedish kid), of uncertain origin.
Extended meaning "child" is first recorded as slang 1590s, established in informal usage by 1840s. Applied to skillful young thieves and pugilists at least since 1812. Kid stuff "something easy" is from 1913 (the phrase was in use about that time in reference to vaudeville acts or advertisements featuring children, and to child-oriented features in newspapers).
In clothing, "made of soft leather," as though from the skin of a kid, but commercially often of other skins. Hence kid glove "a glove made of kidskin leather" is from 1680s; sense of "characterized by wearing kid gloves," therefore "dainty, delicate" is from 1856.
suffix in pet proper names (such as Johnny, Kitty), first recorded in Scottish c. 1400; according to OED it became frequent in English 15c.-16c. Extension to surnames seems to date from c. 1940. Use with common nouns seems to have begun in Scottish with laddie (1546) and become popular in English due to Burns' poems, but the same formation appears to be represented much earlier in baby and puppy.
<a href="https://www.etymonline.com/word/kiddy">Etymology of kiddy by etymonline</a>
Harper, D. (n.d.). Etymology of kiddy. Online Etymology Dictionary. Retrieved $(datetime), from https://www.etymonline.com/word/kiddy