SILLY  , weakly foolish, stupid . This is the current sense of a word which has much changed its meaning . The O.E. sxlig (usually gescelig) meant prosperous, happy, and was formed from srel,

time, season, hence happiness, cf . Icel. stela, bliss; Ger. selig, blessed, happy, &c., probably also allied to Lat. salvus, whole, safe . The development of meaning is happy, blessed, innocent or simple, thence helpless, weak, and so foolish . The old provincial and Scottish word for a caul (q.v.) was " silly-how," i.e . " lucky cap." The development of meaning of " simple," literally " onefold " (Lat. simplex), plain, artless, hence unlearned, foolish, is somewhat parallel . A special meaning of " simple," in the sense of medicinal herbs, is due to the supposition that each herb had its own particular or simple medicinal value .