Michiton or Nichil?

[eggyk]

what is "sound shift (d/t)"? any evidence?

In many languages, the sounds for "d" and "t" are indistinguishable even today. For example, in dutch "geleerd" and "leert" end with effectively the same sound. 

Over time there are consonant shifts, and a "d/t" shift is very common. You can see the evidence of this when looking at words in german vs dutch and english. Where german uses the t, dutch and english have shifted to a d. 

tag -> dag / day
tier -> dier 
gut -> goed -> good