The word brillig was coined by Lewis Carroll in his poem "Jabberwocky" from Through the Looking-Glass. According to Misch-Masch, a handwritten magazine produced by Carroll in 1855 for his family and friends, "bryllyg is 'the time of broiling dinner, i.e. the close of the afternoon." It is derived from the verb to BRYL or BROIL. Note that in Misch-Masch bryllyg is spelt with two ys rather than with two is as were used later in the published version of Looking-Glass.

Humpty Dumpty (in chapter 6 of Through the Looking-Glass) agrees with the definition given by Carroll in 'Misch-Masch' when he states, " 'Brillig' means four o'clock in the afternoon—the time when you begin 'broiling things for dinner'."