Meaning

noun the transfer of heat through a fluid (liquid or gas) caused by molecular motion

noun (meteorology) the vertical movement of heat or other properties by massive motion within the atmosphere

originFrom Latin convectiōnem, from convectiō (“act of carrying”), from convect-, past participle stem of convehō (“to carry together”), combination of com- and vehō. By surface analysis, convect + -ion.

Etymology from Wiktionary, CC BY-SA 3.0