socks and knocks
n.pl.— «Sulfur is capable of forming more than one oxide…, conveniently lumped together with the symbol SOx. Similarly, nitrogen can produce more than one oxide; they are lumped together as NOx.…Sometimes the generic symbol R is used to represent the metallic elements (such as silicon, aluminum, and iron) present in the various constituents of ash. Then the notation ROx can be taken as a symbol for ash. It’s then possible to refer to the potential pollutants as socks, knocks, and rocks.» —by Harold H. Schobert Energy and Society: An Introduction Oct. 1, 2001. (source: Double-Tongued Dictionary)