Ancillary derives from the English word ancilla, a rare word that means "an aid to achieving or mastering something difficult." That word derives from Latin, in which it means "female servant." While English ancilla is unlikely to be encountered except in very specialized contexts (such as philosophy or quantum computing), ancillary picks up on the notion of providing aid or support in a way that supplements something else. In particular, the word often describes something that is in a position of secondary importance, such as the "ancillary products in a company's line."