Making someone happy or pleased; the present participle of 'glad' when used as a verb.
From the verb form of 'glad' plus the '-ing' suffix; 'glad' as a verb is archaic but appears in Middle English texts meaning to make bright or cheerful.
While 'gladding' is rare today, it appears in Renaissance poetry where making someone glad was considered an art—it suggests the idea that happiness is something you create for others, not just feel alone.
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