etymology of "wise"

O.E. wis, from P.Gmc. wisaz (cf. O.S., O.Fris. wis, O.N. viss, Du. wijs, Ger. weise "wise"), from pp. adj. *wittos of PIE base *woid-/weid-/*wid- "to see," hence "to know" (see vision). Slang meaning "aware, cunning" first attested 1896. Related to the source of O.E. witan "to know, wit."

Wise guy is attested from 1896, Amer.Eng. Wisenheimer, with mock German or Yiddish surname suffix, first recorded 1904.

wizen

O.E. wisnian, weosnian "to wither," cognate with O.N. visna, O.H.G. wesanen "to dry up, shrivel, wither;" Ger. verwesen "to decay, rot."

This looks as though "wise" and "wizened" have different sources, assuming that the etymology given is solid, and I have no idea how to evaluate that.

Also, even if the etymology is correct, I can imagine similar sounding words with related meanings affecting each other in use.

For what it's worth, Google recognizes "wisened up", but I don't think I'd ever run into it before. I'm used to "wised up".