“Labile” developed in Middle English, but its roots are found in the Latin words “labilis” and “labi” (“to fall”). In the mid-15th century, “labile” was used in the sense of “liable to err or to sin,” but that usage has shifted in our more secular culture. Today the word can be used in a sense of anything easily altered, or in a more emotionally volatile usage. There’s also a third usage for “labile” that applies specifically to chemistry and chemical bonds: “easily broken down or displaced.”