My investigation combines Classical Philology and historical linguistics. In several Indo-European languages, such as Greek, Armenian, Phrygian, Sanskrit and Iranian, the past tense form was built not only by using special endings but also by adding a prefix to the verbal form. This prefix is called the “augment” in Classical Philology and Indo-European scholarship. It was mandatory in Phrygian, in classical Greek and classical Sanskrit, but in the oldest forms of the languages mentioned above (the Rig Veda in Vedic Sanskrit and the Gathas in Iranian, both from the 2nd Millennium BC), it seemed optional, metrically motivated or was missing altogether. My investigation intends to determine where this prefix comes from, what its original meaning was and how it became obligatory in Greek. My hypothesis is that the augment was in origin an independent particle with both deictic and temporal meaning, that its use and absence can be explained by syntactic and semantic rules and constraints and that the metrical requirement played only a limited role. To check this, I will list, tag and analyse the past tense forms in the oldest texts in Greek (the Mycenaean tablets from the 13th century BC, epic Greek from the 8th century BC, elegiac and lyric poetry until the 5th century BC) and discuss all possible factors influencing the use and absence.