Lewis & Short

pūlēĭum or pūlĕgĭum (Ser. Samm. 1, 18; Cels. 2, 32, 2), ii, n., fleabane, fleawort, pennyroyal: mentha pulegium, Linn.; Plin. 20, 14, 54, § 152; Cic. Div. 2, 14, 33; Col. 12, 35 fin.; 12, 57, 1; Pall. 12, 22, 1; Mart. 12, 32, 19; Ser. Samm. 1, 18.
On account of its pleasant odor, transf.: ad cujus rutam pulegio mihi tui sermonis utendum, i. e. the pleasantness of your discourse, Cic. Fam. 16, 23, 2.