hiss v.

late 14c., of imitative origin. Compare Danish hysse, German zischen, etc. Johnson wrote, "it is remarkable, that this word cannot be pronounced without making the noise which it signifies." Earlier in Middle English ciss, siss was used of a snake's sound (early 14c.). Related: Hissed; hissing.

"a continued 's' sound, commonly expressing disapproval or contempt," 1510s, from hiss (v.).