oat [OE] Oats are used as feed for horses, making them friskier and more energetic, and if you show signs of being lively and buoyant you may be said to be feeling your oats [M19th]. To be off your oats [L19th], on the other hand, means that you have no appetite for food. Wild oats are weeds found in cornfields which resemble cultivated oats. They have no value as a crop, so you would be wasting your time sowing them instead of good grain. Since the 16th century sowing your wild oats has been a term for behaving wildly or promiscuously when young, while to get your oats [1920s] is to have sex.