They originate from the KC-135. They enable the pilot the see the underside of a tanker aircraft when they are flight re-fueling. On the 737? I hear you say! The KC-135, 707, 727 and 737 share the same structure for the cockpit area. Boeing never likes to radicaly change a design so the eyebrows have stayed. Finaly last year they removed them. They are a pain in the backside to change because it will take two men all shift to change one and it blocks up the flightdeck with a body too!
Also notice that they are fitted to the DC-8 as MDC tried to sell them USAF as transporters too. As the DC-9 and MD-80 share the same cockpit structure that explains them aswell.

Rgds Cking

Rgds Cking