Feeling one’s oats describes someone who is energized, enthusiastic even assertive. The phrase was originally used to describe a horse’s energetic behavior after being fed oats. The origins of the phrase are unknown but are found in English literature by the mid 1500’s.
“That wilfull and vnruly age, which lacketh rypenes and discretion, and (as wee saye) hath now sowed all theyr wyeld Oates.” Thomas Newton, “Lemnie’s Touchstone of complexions” 1576.
Illustration “Bucking Horse and Cowgirl” by Charles Marion Russell