Lewis & Short

mulgĕo, si, sum or ctum, 2, v. a. [Sanscr marǵ, wipe or rub away; Gr. ἀ-μέλγω; Germ. melken; Engl. milk], to milk: oves, Verg. E. 3, 5: capras, Plin. 10, 39, 56, § 115.
Absol.: mulgent ad caseum faciendum, Varr. R. R. 2, 11, 4.
Prov.: mulgere hircos, of something impossible, Verg. E. 3, 91.