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 phrase ‘to be yellow’ or ‘to be yellow-bellied’ (to be a coward) seems to enter English first in the 19th century in America. The origin of the phrase is unknown.
In his etymological hoax, How The Irish Invented Slang, Daniel Cassidy claimed an Irish origin for the expression. He said that it comes from the Irish éalú, which is the verbal noun of a verb meaning to escape, to abscond or to steal up on. This is ridiculously improbable. Irish has many good ways of talking about bravery or cowardice but you wouldn’t talk about someone being ‘an escape person’.
By a strange irony, the origin of the expression could conceivably be found in the Irish language but it has nothing to do with éalú. The fact is that in Irish, you can say of someone who is a coward that they have ‘yellow clay in them’ – tá cré bhuí ann. I have always assumed that this means that the pot or whatever you are making is weaker if an inferior kind of clay is found in it, so it breaks up when fired or subjected to any kind of pressure. There is a pretty good case for saying that this phrase explains the origin of the expression yellow for cowardice in English. If Cassidy had known any Irish, he would perhaps have been able to make a reasonable argument for this one.