The Hebrew noun eleph means a thousand and also a clan or family unit. In ancient Israel the 'thousand' was both a numerical quantity and a social/military subdivision of a tribe. The dual meaning reflects how Israelite society organized itself — the clan was the basic fighting and social unit.
Deuteronomy 7:9 speaks of God keeping covenant 'to a thousand generations,' emphasizing inexhaustible faithfulness. Psalm 90:4 — 'A thousand years in your sight are like a day' — where eleph measures divine eternal perspective over human time.