"a champion, one who fights on behalf of another," by 1905, from Latinized form of Greek promakhos "a deity (especially Athene or Apollo) who fights before some person, army, or state as a protector or guardian," from pro "before" (see pro-) + makhesthai "to fight" (see -machy). The word is attested from 1871 in reference to the colossal bronze statue of Athene Promachos that stood in the Athenian citadel.
1620s, "sham-fight for exercise or practice," from Latinized form of Greek skiamakhia "shadow-fighting, a sham fight," from skia "shade, shadow" (see Ascians) + makhē "battle" (see -machy). The notion in the Greek word is said sometimes to be "fighting in the shade" (i.e. practicing in school; ancient teachers taught in shaded public places such as porches and groves), but it seems also to have had a sense of "fighting with shadows, shadow-boxing." In English, often figurative, of futile combat with an imaginary enemy.