What is the origin of the "iso [frequency/voltage/power]" terminology?
Iso is a Greek-derived prefix meaning &quot;equal&quot;, with a pretty substantial history of use in scientific and mathematical contexts to mean &quot;the same&quot; (isomolar, isotropic, isostructure, isomorphism), or a line or surface along which some quantity is held constant (isobar, isotherm, isochron, isocline).
The name ISO is officially not an acronym (none of its official names start with those letters in that order, although its English name, &quot;International Organization for Standardization&quot;, comes close); instead it's a pun on iso and the organization's role in promoting uniformity around the world.