libra = balance/scales (for weighing). Also, it was a unit of weight in ancient Rome. “liber” is a masculine noun of the 2nd declension and thus has no gramma

libra = balance/scales (for weighing). Also, it was a unit of weight in ancient Rome. “liber” is a masculine noun of the 2nd declension and thus has no grammatically sensible connection to “libra” which is a feminine noun of the 1st declension.