This article is expressing that "Qayin" derived from the 1st millenium BC South Arabic word Qyn, and that Cain is not a name old enough in Bible times of the 2nd millenium. Is it plausible that this is in fact a correct approach?
Hess was able to identify qyn as an "administrator's title" in Old South Arabic inscriptions, it appearing in Sabaean and Qatabanian inscriptions of the 1st millennium BCE. He also noted that epigraphic sources for the Old South Arabian inscriptions do not exist for 2d millennium BCE times. On the basis of the present evidence, Hess concluded that Cain (Hebrew qyn) if derived from South Arabic qyn, ( qyn meaning a "metal smith" in later South Arabic) indicated that Genesis' Cain could be no older than the mid-first millenium BCE.
A third suggestion derives from the lexica of Old South Arabic. This is the qyn root used for the title of an administrator. The term appears both in Sabaean and in Qatabanian. A root qyn has been found in personal names in Old South Arabic inscriptions, including a qynw who appears as a Qedarite ruler in a 5th century BC Aramaic inscription from Tell el-Maskuteh at the entrance to Wadi Tumilat."
"Studies have placed Cain in particular geographical and chronological contexts in the Ancient Near East. The figure of Cain has been associated with the region south of ancient Israel, i.e., the modern Negev and the Arabian peninsula. In part, this is because (as noted above) the qyn root occurs in names of persons in South Arabian tribes of the first millenium. It does not occur in the second millennium. Both the geographical and chronological parameters on this name should allow us to locate specifically in first millennium South Arabia."