Mae, also spelled May, is a variant of Mary. As Mary is associated with Motherhood( in fact divine Motherhood) it is conceivable that Mae Mae might indicated ( Grandmother) but I have never heard it in this context.
In England, Mae means variation of may, month name. In France, Mae means may. In Roman mythology Maia: (source of the month May) was goddess of spring growth. In Hebrew usage, Mae means bitter.