Viz.
A contraction of videlicet. The z is a corruption of 3, a common mark of contraction in the Middle Ages; as hab3—i.e. habet; omnib3—i.e. omnibus; vi3—i.e. videlicct.
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Entry taken from Dictionary of Phrase and Fable, edited by the Rev. E. Cobham Brewer, LL.D. and revised in 1895.