The aircraft experienced a sudden uncommanded left yaw 10-15 knots below the V1 speed of 130 knots. The crew controlled the aircraft and rejected the take off. The flight attendants seated in the rear of the aircraft confirmed the yaw was very abrupt. The DFDR while recording the event did not disclose any information as to the origin of the signal that commanded the input that initiated the yaw. However the DFDR did disclose that the yaw was not a result of flight control input, therefore it is suspected that brake or nose wheel steering inputs may have been responsible. Parameters for these systems are not recorded on the DFDR. The company has introduced a strongly worded briefing to passengers about the dangers of operating electronic equipment during critical stages of flight although there was no evidence that this was the cause of this incident.