Word Studies Chapter 20
20:2. ‘Thousand year(s)’
Greek #5507 chiliŏi ‘plural of uncertain affinity’, ‘thousand’.
Hebrew #505 ’eleph, ‘the first letter of the alphabet, eventually used as the numeral one thousand’.
See also Psalm 68:17. ‘Thousand years’. BDB p. 1041. ‘Thousands of repetitions, i.e., thousands twice told.’