An Etymological Dictionary of Astronomy and Astrophysics
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One of the seven stars of the → Big Dipper, which links Ursa Major's tail to the Bear's hindquarters. Megrez is the dimmest of the Big Dipper stars at magnitude +3.3. It is an A3 dwarf, about 20 times more luminous that the Sun, lying 81 light-years away.

From Ar. al-Maghriz(المغرز) "the root, base, bottom" (of the Bear's tail).