'Pound' comes from Latin 'pondo' (by weight) — and 'lb.' comes from 'libra,' the other half of the phrase.
A unit of weight equal to 16 ounces (approximately 0.454 kilograms); the basic monetary unit of the United Kingdom, equal to 100 pence; also (verb, separate etymology) to strike repeatedly with heavy blows.
The weight/currency 'pound' comes from Old English 'pund,' from Proto-Germanic '*punda-,' borrowed very early from Latin 'pondo' (by weight, a pound), an ablative form of 'pondus' (weight), from 'pendere' (to weigh, to hang). The phrase 'libra pondo' (a pound by weight) gave English both 'pound' (from 'pondo') and the abbreviation 'lb.' (from 'libra'). The monetary pound originated because a pound of sterling silver was the basis for the currency. Note: the verb 'pound' (to strike heavily) has a separate Germanic etymology. Key
The abbreviation 'lb.' for pound comes from Latin 'libra' (a balance, a unit of weight), not from 'pondo.' The full Latin phrase was 'libra pondo' — 'a pound by weight.' English took the word 'pound' from 'pondo' but the abbreviation from 'libra.' Meanwhile, 'Libra' the zodiac sign is the same Latin word — the scales, the balance — which is why Libra's symbol is a balance scale. Weight, currency