bachelor (n.) Look up bachelor at Dictionary.com
c.1300, "young man;" also "youthful knight, novice in arms," from Old French bacheler, bachelor, bachelier (11c.) "knight bachelor," a young squire in training for knighthood, also "young man; unmarried man," and as a university title, of uncertain origin, perhaps from Medieval Latin baccalarius "vassal farmer, adult serf without a landholding," one who helps or tends a baccalaria "field or land in the lord's demesne" (according to old French sources, perhaps from an alteration of vacca "a cow" and originally "grazing land" [Kitchin]). Or from Latin baculum "a stick," because the squire would practice with a staff, not a sword. "Perhaps several independent words have become confused in form" [Century Dictionary]. Meaning in English expanded early 14c. to "young unmarried man," late 14c. to "one who has taken the lowest degree in a university." Bachelor party as a pre-wedding ritual is from 1882.