Archaic KJV Word
Wist
Modern equivalent: knew
What Was Lost
Moses's holy ignorance. Moses 'wist not that his face shone' -- he was unaware that encounter with God had visibly transformed him. The word captured the beautiful unconsciousness of genuine holiness: Moses did not know he was radiant. Jesus's 'wist ye not?' was a gentle rebuke of Mary and Joseph's unawareness of what they should have known.
Closest Survivor in Modern English
unwitting (not knowing/unaware -- the negative form preserves the root)
Peak Usage (1611)
KJV Exodus 34:29 -- 'Moses wist not that the skin of his face shone'; Luke 2:49 -- 'Wist ye not that I must be about my Father's business?'
Died ~1700
The past tense of 'wit' (to know) died as 'wit' lost its verb form. Only 'wisdom,' 'witness,' and 'wits' survive as fossils of the once-central verb 'to know.'
What Replaced It
“knew”
Generic; wist carried the specific sense of conscious awareness -- not just having knowledge but being aware
“realized”
Implies a dawning process; wist was binary -- you either wist or you did not