1638, from L. formula "form, rule, method, formula," lit. "small form," dim. of forma "form." Originally, "words used in a ceremony or ritual." Modern sense is colored by Carlyle's use of the word for "rule slavishly followed without understanding" (1837). Formulaic is from 1882; formulate is 1860.
"Men who try to speak what they believe, are naked men fighting men quilted sevenfold in formulae." [Charles Kingsley, "Letters," 1861]