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We analyze eight epochs of Hubble Space Telescope H$\alpha$+[N II] imaging ofEta Carinae's outer ejecta. Proper motions of nearly 800 knots reveal that thedetected ejecta are divided into three apparent age groups, dating to around1250 A.D., to around 1550 A.D., and to during or shortly before the GreatEruption of the 1840s. Ejecta from these groups reside in different locationsand provide a firm constraint that Eta Car experienced multiple major eruptionsprior to the 19th century. The 1250 and 1550 events did not share the sameaxisymmetry as the Homunculus; the 1250 event was particularly asymmetric, evenone-sided. In addition, the ejecta in the S ridge, which have been associatedwith the Great Eruption, appear to predate the ejection of the Homunculus byseveral decades. We detect essentially ballistic expansion across multipleepochs. We find no evidence for large-scale deceleration of the observed knotsthat could power the soft X-ray shell by plowing into surrounding material,suggesting that the observed X-rays arise instead from fast, rarefied ejectafrom the 1840s overtaking the older dense knots. Early deceleration andsubsequent coasting cannot explain the origin of the older outerejecta---significant episodic mass loss prior to the 19th century is required.The timescale and geometry of the past eruptions provide important constraintsfor any theoretical physical mechanisms driving Eta Car's behavior.Non-repeating mechanisms such as the merger of a close binary in a triplesystem would require additional complexities to explain the observations.

Ancient eruptions of Eta Carinae: A tale written in proper motions