1849, said to be originally a hobo term (but attested in London underclass from 1851), of uncertain origin; perhaps from monk (monks and nuns take new names with their vows, and early 19c. British tramps referred to themselves as in the monkery). Its origins seem always to have been obscure:
Labile is an adjective used to describe something that is easily or frequently changed. Radioactive elements, such as uranium or plutonium, are labile. It is this lability that makes them unstable and dangerous. From the Latin verb lÄbÄ«, to slide or slip, labile is often found in a technical context, especially in science, to refer to some sort of instability. For example, in chemistry, a compound that can be easily broken down by heat is called labile.
Brittle Diabetes (Labile Diabetes) Brittle diabetes mellitus (or labile diabetes) is a term used to describe particularly hard to control type 1 diabetes. Those people who have brittle diabetes will experience frequent, extreme swings in blood glucose levels, causing hyperglycemia or hypoglycemia.