Pronunciation: [ˌɒn slˈa͡ɪ] (IPA) 
The correct spelling of the phrase "on sly" is actually "on the sly". Phonetically, it is pronounced as /ɒn ðə slaɪ/. The word "sly" is an adjective meaning cunning or deceitful. When used in the phrase "on the sly", it means secretly or without others knowing. It is important to use the correct spelling and pronunciation to avoid confusion and ensure clear communication.
On the sly is an idiomatic expression that means doing something discreetly, secretly, or without others noticing. It refers to engaging in an activity or a behavior behind someone's back or without their knowledge. When someone acts on the sly, they do it in a cunning or crafty manner, typically to avoid getting caught or to maintain secrecy. This phrase suggests a sense of mischief or deceitfulness, as one tries to conceal their actions or intentions to achieve their desired outcome.
The phrase "on the sly" is often used to describe actions that are not necessarily morally wrong but are done in a sneaky, underhanded, or unauthorized way. It can be applied in various contexts, such as cheating on a test, secretly snacking on forbidden food, conducting a secret investigation, or engaging in a clandestine romantic affair. The emphasis is generally on the secrecy and the intention to go unnoticed or undiscovered.
The term "on the sly" originates from the word "sly," meaning shrewd, cunning, or deceitful. By adding "on" to the phrase, it conveys the concept of performing an action in a manner that is cunningly concealed from others, thereby reinforcing the element of deceit or trickery.
The phrase "on sly" is derived from the Middle English word "sli" or "sly", which meant cunning, crafty, or secretive. It originated from the Old Norse word "slægr" with a similar meaning. Over time, "sly" became associated with acting in a quiet and unobtrusive manner, often to achieve a hidden or personal agenda. When the word "sly" is combined with the preposition "on", it forms the phrase "on sly", meaning to do something secretly, discreetly, or without drawing attention to oneself.
