The XKCD comic is only partially correct. Depending on what source you believe English text has about 0.6 to 2.3 bits of entropy per character. This means you need somewhere between 4.7 and 18.3 characters in each word to reach 11 bits of entropy per word. Assuming entropy is closer to 2 bits per character this is a realistic situation. However, when you assume entropy is closer to 1 bit per character the words have to be too long to be realistic.