secret; furtive; sneaky
He and she kept up a surreptitious correspondence for several months, until his sister intercepted one of her letters.
sub (under, up to)#rapere (to seize, carry off) (Latin)
surreptitious sounds like sir repeated it to us. - only to us and not to everyone as it was a secret method to solve the problem. Surreptitious sounds like suspicious. you suspect someone if they are hiding secrets