The etymology given for Hedwig should instead be here, however that particular etymology is incorrect (as is the name Hadewig). The real name is Haduwig, from the Proto Norse haþu "battle" and the Old Norse víg "fight/battle", in turn from the Ancient Germanic wīg (same meaning). In handwriting, a ð (ðat/eð) could be mistaken for a d, and thus when spoken it would change the overall pronunciation of the name. The þ (thorn/þurz) is a voiceless "th" sound, as in "thaw", whilst the ðat/eð is a voiced "th" sound, as in "the".
In handwriting, a ð (ðat/eð) could be mistaken for a d, and thus when spoken it would change the overall pronunciation of the name. The þ (thorn/þurz) is a voiceless "th" sound, as in "thaw", whilst the ðat/eð is a voiced "th" sound, as in "the".