wily comes from wile + -y; wile is from Middle English wile ('trick, stratagem'), probably from Old Norse vél ('trick, craft') or related to Old English wīġlian ('to practise divination'). Morphologically, the word is transparent: -y is attached to the older base named in the history, so the modern form packages an inherited or borrowed stem inside a later English derivative. In modern use, the adjective sense is "skilled at gaining an advantage through cunning or trickery", which keeps the etymology connected to the word's present dictionary value rather than treating it as a merely historical label. The wider word family includes related English forms such as wile, guile and derivatives such as wiliness, showing how the same base continues to support neighboring English vocabulary. The principal historical forms in the chain include Middle English wile, Old Norse vél, which anchor the explanation in named linguistic material.