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.
It is hard to understand why Cassidy included this word, except as padding. All the English dictionaries are in agreement that this word derives from the Old Celtic bardos. There is no certainty as to how it came into English from Celtic, as it could have been from Scottish Gaelic, Irish or Welsh and it may have been influenced by Classical writers like Strabo, who wrote that the three branches of the Celtic priesthood were the vates, the bards and the druids. The word bard certainly has nothing to do with slang.
The usual theory now is that the word came into Scots from Scots Gaelic in the 15th century and spread into English.