means The act of holding on to, maintaining, or caring for something or someone — whether possessions, secrets, livestock, or one's word.

from From Old English 'cepan,' to seize, hold, or watch over — a word whose earlier meaning is murky, possibly tied to keeping watch or guard. The '-ing' suffix turns the verb into the ongoing act. Notice how the old sense of 'watching' shaded into 'holding,' so that to keep something was first to keep an eye on it, then to keep it for good.