And where does the minhug of first pouring a drop of water from the becher into the wine/grape juice bottle before then pouring the wine/grape juice into the becher, come from?
The Ta’amei Haminhugim quotes the Elyah Rabbah that wine brings “y’lala” (weeping) to the world; when water is added, it changes it to bracha. He then quotes the S’fas Emes that wine represents gevurah, whereas water represents chessed.