originally the distance from the elbow to the tip of the middle finger (cubit), about 18 inches. Now it is 5 spans, or 45 inches.
later it morphed into a variety of lengths, depending upon the nationality. The Swedish unit is about 2 feet.
► uses
Uses:
he shall taste ten quarters of sorrow in his love, then shall he find for every pint of honey a gallon of gall : for every dram of pleasure, an ounce of pain : for every inch of mirth, an ell of moan.
John Lyly. Euphues: The Anatomy of Wit (1578)
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That the Frost pierces into the Earth, two Cubits or Swedish Ells; and what moisture is found in it, is white, like Ice: That Waters, if standing, freeze to a greater depth, even to three such Ells or more; but those that have a Current, less: That rapid Rivers freeze not at all; nor ever-bubling Springs; and that these latter seem even to be warmer in Winter, than Summer.
The Royal Society. Philosophical Transactions: Giving Some Accompt of the Present Undertakings, Studies,and Labours of the Ingenious in Many Considerable Parts of the World, volume I (1666)