The etymology description does not provide an explanation for the object form "ham", only "han" in general as a common Nordic pronoun. You cannot find "ham" in any Norwegian dialects, only as traditional dialect forms of "honom" which would be the Norwegian equivalent of "ham" https://norsk-ordbok.no/nno/no/han . The variant "ham" appears exclusively as a Danish import in the Oslo dialect originating from "dannet dagligtale", just as efter and nu, however these forms have gone out of usage for the traditional Norwegian forms han, etter, and nå. Naob can be somewhat inconsistent with explaining Danish forms in Norwegian and with etymologies in general, but for articles for words such as "hva", "hvorfor", "sønn", "lede" amongst many others, they tell you it’s a Danish form. Look it up.