The phrase "didst part" is an archaic way of saying "did part", meaning to separate or divide something. The antonyms, or opposite words, for this phrase would be "unite", "combine", or "merge". These words imply the bringing together of separate components to form a cohesive whole. Other antonyms for "didst part" could include "join", "connect", or "attach", as these words imply a linking of separate entities to create a unified whole. In essence, the antonyms for "didst part" all involve some form of unification or integration, as opposed to the separation and division implied by the original phrase.