Dripstick and dipstick are 2 different methods (for different circumstances) of measuring fluid levels.

Take a tank with an opening at the top, like a filler tube. Dip a stick into the top-hole, draw it out, look at the fluid level on the stick, use that information (how much depth from top of tank to top of fluid) to estimate the volume of fluid in the container (typically using a pre-calculated table of measurements).

An aircraft wing-tank has no hole in the top to drop a dipstick into.

Instead, it is equipped with a hollow tube that goes UP from the bottom of the wing to the inside top of the tank. Unlatch the cover and slowly draw the tube down until fuel starts to drip (which is why it is a drip-stick) from the dependent opening. Note the measurement mark on the tube. Compare it to the calibrated chart to give the fuel amount in the tank.

jimdoc@...