For some time now, some of my on-line friends have advised me to provide a version of CassidySlangScam without the invective aimed at Cassidy and his supporters. In response to that advice, I am working on providing a glossary of the terms in Cassidy’s ludicrous book How The Irish Invented Slang with a short, simple and business-like explanation of why Cassidy’s version is wrong.
The word kid, meaning a young goat, entered the English language a long time ago from Old Norse. It acquired the meaning of child in informal contexts around the year 1590.
Daniel Cassidy, in his work of false etymologies, How The Irish Invented Slang, claimed that the word kid comes from the Irish word cuid. In order to make a case for this, he homes in on several meanings of the word cuid that suggest a link with endearment and children:
“Cuid (pron. kid, cuid, kidj), n., share, part, portion; a term of endearment, love, affection. A chuid (pron. a khid), my dear; mo chuid de’n tsaoghal (pron. mo khid den tael), all I have, my darling; a chuid inghean (pron. a khid inyian), his daughters; a chuidín (pron. a khidín, a khijín), my little dear. (Dineen, 281, 282; Foclóir Póca, 326.)”
In fact, cuid is one of the most widely-used words in the Irish language. It is not pronounced like kid, as you can hear in the sound files on focloir.ie which are given in the three main dialects of Irish, Ulster, Connaught and Munster:
https://www.focloir.ie/en/dictionary/ei/bit#bit__3
You can also find a full description of its uses here, as given by Ó Dónaill:
https://www.teanglann.ie/en/fgb/cuid
As you can see, cuid can be used in phrases like mo chuid éadaigh (my part of cloth, my clothes), ith do chuid (eat your portion, your food), a gcuid airgid (their part of money, their money), a cuid Gaeilge (her part of Irish, her Irish). It can even mean sex, as in the phrase Bhí cuid aige di (= He had it off with her).
English kid does not derive from the Irish word cuid, which, apart from one phrase (a chuid) has nothing to do with affection or love. The English word kid meaning child derives from the English word meaning a young goat, as any sensible person already knew.