'Secret' is Latin for 'sifted apart' — from 'cernere' (to sieve). Kin to 'crisis' and 'certain.'
Something that is kept or meant to be kept unknown or unseen by others.
From Old French 'secret,' from Latin 'sēcrētum' (a secret, a hidden thing), noun use of the past participle of 'sēcernere' (to set apart, to separate, to distinguish), from 'sē-' (apart) + 'cernere' (to sift, to separate, to distinguish), from PIE *krey- (to sieve, to separate). A secret was originally 'something set apart' — separated from common knowledge. The same root produced 'certain,' 'concern,' 'discern,' 'crime,' and 'crisis.' Key roots: *krey- (Proto-Indo-European: "to sieve, to separate, to distinguish").
'Secret,' 'certain,' 'crime,' 'crisis,' and 'discern' all come from PIE *krey- (to sieve, to separate). A secret is 'set apart.' Certainty is 'what has been sifted out.' A crime is a 'judgment of guilt' (something separated as wrong). A crisis is 'a moment of separation.' Discernment is 'sifting things apart.' Knowledge, in Indo-European, was the act