wiseacre: [16] Wiseacre has no etymological connection with acres. The word’s ancestral meaning is ‘person who sees or knows things, prophet’. It was borrowed from Middle Dutch wijsseggher, which denoted ‘soothsayer’ (with no derogatory connotations). And this in turn came from Old High German wīssago, an alteration (due to the similarity of wīs ‘wise’ and sagen ‘say’) of wīzago ‘prophet’, which was derived from the prehistoric Germanic base *wīt- ‘know’ (source of English wise and wit).
wiseacre (n.)
1590s, partial translation of Middle Dutch wijssegger "soothsayer" (with no derogatory connotation), probably altered by association with Middle Dutch segger "sayer" from Old High German wizzago "prophet," from wizzan "to know," from Proto-Germanic *wit- "to know" (see wit (v.)). The deprecatory sense of "one who pretends to know everything" may have come through confusion with obsolete English segger "sayer," which also had a sense of "braggart" (mid-15c.).