Lewis & Short

2. pōpŭlus, i, f. [root pamp-, pap-, to swell; Lat. papula, papilla, pampinus], a poplar, poplar-tree, Plin. 16, 23, 35, § 85; 16, 18, 31, § 77; 17, 11, 15, § 78; Ov. H. 5, 27; sacred to Hercules, Verg. E. 7, 61; Ov. H. 9, 64; Plin. 12, 1, 2, § 3: alba, the silver-poplar, Hor. C. 2, 3, 9.