Any percentage changes in a stock price will result in an equal percentage change in a company's value. This is the reason why investors are so concerned with stock prices and any changes that may occur since a $0.10 drop in a $5 stock can result in a $100,000 loss for shareholders with one million shares.
The primary meaning of libra was balance or scales (as in the astrological sign), but it also stood for the ancient Roman unit of measure libra pondo, meaning a pound by weight.. We got the word pound in English from the pondo part of the libra pondo but our abbreviation comes from the libra.
'pound' is short for 'pound weight' which was libra pondo in Latin. The libra part meant both weight or balance scales. The Latin usage was shortened to libra, which naturally was abbreviated 'lb'.