19th-century coinage (introduced by W. J. M. Rankine in the 1860s) based onAncient Greekἀδιάβατος(adiábatos,“impassable”), used of terrain (rivers, forests) by Xenophon, fromἀ-(a-,“not”) +διά(diá,“through”) +βατός(batós,“passable”), fromβαίνω(baínō,“to go”).
The line drawn on the indicator diagram in the latter case has been named by Professor Rankine anAdiabatic line, because it is defined by the condition that heat is not allowed to pass through (διαβαίνειν) the vessel which confines the substance.
