sextant: [17] A sextant is etymologically an instrument based on a ‘sixth’ of a circle. Sextants measure off the angle between the horizon and a celestial body on a graduated scale that is marked on an arc equal to one sixth of a circle. They were first named at the beginning of the 17th century by the Danish astronomer Tycho Brahe, who used the term sextāns ‘sixth part’, a derivative of Latin sextus ‘sixth’ (to which English six is closely related). The anglicized version sextant is first recorded in 1628. => six
instrument for determining latitude, 1620s, from Modern Latin sextans, said to have been coined c. 1600 by Danish astronomer Tycho Brahe, from Latin sextans "a sixth," from sex "six" (see six). So called because the sextans has a graduated arc equal to a sixth part of a circle.
