An Etymological Dictionary of Astronomy and Astrophysics

1. Useful part of the received information that can be distinguished from noise.
   

2. Information transmitted by means of a modulated current or an electromagnetic wave and received by telephone, radio, television, etc.

Etymology (EN): M.E., from O.Fr. signal, from M.L. signale “a signal,” from L.L. signalis (adj.) “used as a signal, pertaining to a sign,” from L. signum “signal, sign.”

Etymology (PE): Nešâl, from neš- base of nešân meaning → sign + -âl, → -al.