"DOC" represents phases of the Moon by shape: "D" is the waxing moon; "O" the full moon; and "C" the waning moon. In the Southern hemisphere, this is reversed, and the mnemonic is "COD". A French mnemonic is that the waxing moon at its first "premier" quarter phase looks like a 'p', and the waning moon at its last "dernier" quarter looks like a 'd'. In German, the Moon is compared to a handwritten small letter a for "Abnehmen" (waning) and a z for "Zunehmen" (waxing). One more (Northern hemisphere) mnemonic, which works for most Romance languages, says that the Moon is a liar: it spells "C", as in crescere (Italian for "to grow") when it wanes, and "D" as in decrescere ("decrease") when it waxes.
