The term 'An Early Form of Sextant' refers to two instruments used in navigation: the BEBOP and the astrolabe. The BEBOP is a five-letter word which was an early form of sextant used by sailors in the 16th century. It was a simple instrument consisting of a wooden frame with two arms, each arm having a sighting device at one end. The other end of the arms were connected to a plumb line, which was used to measure the angle of the sun or stars. The astrolabe is a nine-letter word which was also an early form of sextant used by sailors in the 16th century. It was a more complex instrument consisting of a rotating disc with a graduated scale, which could be used to measure the altitude of the sun or stars. Both the BEBOP and the astrolabe were used to help sailors navigate the seas and find their way back home.