A320 Captain reported the aircraft veered uncontrollably left during takeoff possibly due to engine failure resulting in a rejected takeoff.

Narrative

Cleared for Takeoff [runway] XXL ZZZ [airport]; winds were from the West at 9 kts. Captain was PF. First Officer was on first leg of Operating Experience (OE). The Jumpseater was on his observation for new Line Check Pilot (LCP) training. I advanced the throttles to 50 percent N1; engines spooled up evenly and were stable. I advanced the throttles to the FLEX position. Standard callouts were made along with SOP Flight Mode Annunciator (FMA) callouts. No irregularities were noted. Estimated around 90kts there was an aggressive uncommand yaw to the left that did not decrease. The aircraft was heading towards the left edge of the runway. I elected to reject the takeoff. When I felt the yaw to the left; I immediately looked at my engine instruments; all were normal and synced. It felt like an engine failure. The Auto brakes did engage. once I had the aircraft under control I dis-engaged the auto brakes and made a right turn onto taxiway 1 and then another right turn heading North on taxiway 2 where we ran our checklists and made the appropriate calls to operations; Dispatch and maintenance. All of the appropriate PA announcements were made. After talking with Maintenance Control a decision was made to go back to the gate. Once we were off the active runway all 3 pilots discussed the event. None of us saw any type of irregularity with the engines nor did we feel any type of wind gust. We had Dead Heading pilots in the passenger cabin. I asked them if they felt the yaw and they both said Yes" thinking it was an engine failure. After the Rejected Takeoff (RTO) ZZZ tower told us they had not seen any type of a wind gust. they reported the winds to us at 290/9kts"