I assume everybody here has seen terminology in their own field or others that produced a groan upon seeing it for the first time. My "favorite" is in signal processing. There is a common audio transformation that does a Fourier analysis, takes the absolute value at each frequency, and then the logarithm. Well, the regular FFT gives you a spectrum, so this thing is called ... a Cepstrum. Even worse, when you multiply each frequency value with some function, it's called a Lifter, because you know, it's a Filter on the Cepstrum. *groan* What's your favorite?