What does Boxing Day have to do with boxing?
1809, from hydrogen + -ate (2). Related: Hydrogenated; hydrogenation.
hydrogenation hy·dro·gen·a·tion (hī'drə-jə-nā'shən, hī-drŏj'ə-)n. The addition of hydrogen to a compound, especially to solidify an unsaturated fat or fatty acid.
To treat or combine chemically an unsaturated compound with hydrogen. Liquid vegetable oils are often hydrogenated to turn them into solids.
To turn coal into oil by combining its carbon with hydrogen to form hydrocarbons.