עד ביאת הגואל

The idea of saying Ad Bi'as Go'el is, that when someone is Davening on a Jahrzeit Le'ilui Nishmas his relative, he is told that the seperation between him and his relative who he loves isn't for long, only "Ad Bi'as Go'el", (therefore he answers "Bimheiro Beyomeinu Omen").

We know this was the Minhag at least in the last 100 years, but it is not mentioned in the old Seforim or by the Poskim. You can find it in לקט הקמח החדש in the volume of simonim מו-פח page שי as the Minhag of many places. Rav Shmuel Dovid Munk brings it as a known Minhag (in a booklet of Minhogim called Toras Imecho from the year תשלח). It is also brought by Unna (in Minhogei Edos Ashkenaz).

Michael FRBSH