C. T. Lewis in his Elementary Latin Dictionary posits an early form clibra from which he states that libra (pound) derives. It is from a class of "cli-" words implying tipping, sloping, slanting, etc. He relates libra to the root -cline as seen in decline, recline, inclination, and he considers libro (to balance) a cognate. (C)libra then would have its logic perhaps in the way the pound was originally weighed and standardized, on a balance scale. If he is correct, then libra never was related to the words for book and library; it merely lost its initial "c" and what was left bore an accidental resemblance to liber. Librarium came about by adding the unremarkable collectivizing "-arium" to whatever the collection was: in this case, books. There are a lot of these false positives in the etymology lab, like gunsel and sparrowgrass in English, to name a couple. John Dyson Spanish and Portuguese Indiana University