"Something to do with bicycle pumps, IIRC?"
IIRC the terms were adiabatic expansion - and isothermal expansion. Too long ago to remember the precise definitions - and all the online ones need an icepack to read.
Forcing compressed gas/liquid through a thin nozzle - it cools rapidly as it expands on escaping - the Venturi effect. Old fashioned carburettors can become blocked by ice due to this effect at above-freezing ambient temperatures.
IIRC that is the process to make "freeze dried" instant coffee. Probably also the principle for the refrigerant in fridges and freezers - although that might also involve the latent heat of vaporisation? The latter is how canvas bags hung outside a vehicle will cool the water inside during a journey.
The physics teacher would stand a beaker full of ether in a shallow amount of water in a dish. Air was then bubbled through the ether to cause it to evaporate. The beaker would then cool enough to freeze the water in the dish.