late 14c., "identical in amount, extent, or portion;" early 15c., "even or smooth of surface," from Latin aequalis "uniform, identical, equal," from aequus "level, even, flat; as tall as, on a level with; friendly, kind, just, fair, equitable, impartial; proportionate; calm, tranquil," which is of unknown origin. Parallel formation egal (from Old French egal ) was in use late 14c.-17c. Equal rights is from 1752; by 1854 in American English in reference to men and women. Equal opportunity (adj.) in terms of hiring, etc. is recorded by 1925.
A skeg is employed in the type of kayak used on more open water such as the sea. Its purpose and use are rather different from those of the surfing skeg. In the kayak, the amount of exposure of the skeg to the water, and also its effect on the position of the boat's centre of lateral resistance (CLR), is freely adjustable by the crew. The adjustment varies the degree to which the wind affects the boat - that is, the amount of lateral movement the wind can cause by impacting the upper parts of the boat and the crew.    In more conventional calculations, this would be the centre of effort of the sail area (CE). In still water, where the wind is pushing the boat sideways, a contrary force (lateral resistance) develops, resisting that movement. If the central points of the application of those two forces coincide, the boat moves steadily sideways. Otherwise, it rotates in the horizontal plane, until they are in line. By varying the CLR, it is possible to better control the boat's attitude towards the wind and waves. Irregular flowing movement of the water complicates the issue, however.  This link explains the subtleties of the kayak skeg. They may be made of wood, fiberglass or aluminum. Some are deployed using internal cables, but others use external ropes and bungee cord . Typically, these are retractable, and they are not a rudder.     If properly configured (., use of street sign aluminum in a narrow box that extends through the hull) they will not flex, and will greatly decrease and counter pitch , Roll and yaw , like a centerboard on a sailboat, when the craft is moving. In that sense, the skeg acts as a lifting foil .
Arabian astronomers, following Ptolemy, knew these stars as Al Zubana , the Claws, or, in the dual, Al Zubanatain , degenerating in Western use to the Azubene of the 1515 Almagest ; but later on, when influenced by Rome, they became Al Kiffatan , the Trays of the Balance, and Al Mizan , the Scale-beam, Bayer attributing the latter to the Hebrews. This appeared in the Alfonsine Tables and elsewhere as Almisan , Almizen , Mizin ; Schickard writing it Midsanon . Kircher, however, said that Wazn , Weight, is the word that should be used instead of Zubana ; Riccioli adopting this in his Vazneschemali and Vazneganubi , or Vaznegenubi , respectively applied to the Northern and Southern Scale as well as to their lucidae .