As I know, we can get the cepstrum by taking the Inverse Discrete Fourier Transform (IDFT) of the log of the power spectrum.
And we can get the Mel-frequency cepstral coefficients (MFCCs) by taking the Discrete Cosine Transform (DCT) of the log filterbank energies.
But I didn't understand the following two points:
Why do we use the term "cepstral" in MFCCs when we use DCT instead of IDFT?
How does MFCCs relate to the cepstral domain according to the reference here?