Jamieson, Fausset and Brown on Isaiah 44:14

14. Description of the material out of which the idol is formed.

cypress--rather, from Hebrew root, "to be hard," the holm oak," an evergreen abundant in Palestine [Gesenius].

strengtheneth--literally, "and he getteth strength to himself in the trees of the forest;" that is, he layeth in a great store of timber [Lowth]. Or, "chooseth," as "madest strong for thyself," that is, hast chosen (Psa 80:15, 17) [Gesenius]. But English Version gives a good sense: "strengtheneth"; that is, rears to maturity; a meaning suitable also to the context of Psa 80:15, 17, where Israel is compared to a vine planted by Jehovah [Maurer].

rain doth nourish it--Though the man planted the tree, yet he could not make it grow. In preparing to make an idol, he has to depend on the true God for rain from heaven (Jr 14:22).