2. Immature, featherbrained, lacking common sense: Greg is considered to be a silly person when he says that getting a university education is a waste of time.
3. Descriptive of being foolish, inane, or absurd: That silly joke that Walter told made everyone laugh. 4. Etymology: silly is a spelling variant of an earlier adjective seely, which has long-term roots in Germanic languages.
Its basic sense was "blessed, fortunate", and the meaning of the German selig still has that meaning. The earliest thirteenth-century meanings of seely were "happy, fortunate", "spiritually blessed", and "pious, holy, good".
From these beginnings, it started to be used in the sense of "blameless, innocent", which was often used to express sympathy for those who suffered undeservedly. Those who were innocent victims can also be thought of as deserving pity, and seely was used this way, too; such as, "pitiable, helpless, and defenseless".
Silly has undergone considerable sense development from the original meaning of "happy". The sense of "innocent" is first recorded in about 1200, that of "weak" about 1300, and that of "unfortunate, pitiable", about 1280.
From these senses developed the meanings of "simple, rustic, ignorant", which was first recorded before 1547, and the concept of "lacking in reason" or "sense, foolish", was recorded in 1576.