Lewis & Short

barbŭla, ae. f. dim. [barba].

  1. I. A little beard (as worn by the young Romans; v. barba. barbatus, and barbatulus): non hac barbulā, sed illa horrida, quam in statuis antiquis videmus, * Cic. Cael. 14, 33.
    1. B. Transf. to plants (cf. barba, II. A.), Plin. 27, 11, 74, § 98; 21, 8, 25, § 49.
  2. II. A cognomen of Q. Aemilius, Liv 9, 20, 7.