The Proto-Germanic pluperfect

The Germanic perfect presents (Präteritopräsentien) form a past tense by adding the endings of the weak preterit to the stem of the past participle, e.g. Go. wissa ‘knew’. This is a recent formation (cf. Kortlandt 1989). We may therefore ask ourselves if we can reconstruct the earlier formation which was ousted by the weak preterit. We may also try to recover the motivation for the replacement