the GNU version of the Collaborative International Dictionary of English
ad. With which; -- used relatively.
ad. With what; -- used interrogatively.
n. The necessary means or instrument.
The Century Dictionary and Cyclopedia
With what or whom?
With which; also, as compound relative, that with which.
[Wherewith is colloquially used as a noun iu the phrase the wherewith (compare the commoner equivalent, phrase the wherewithal)—that is, what is necessary or required; means.
Word Usage
"In those days shall Judah be saved, and Jerusalem shall dwell safely: and this is the name wherewith she shall be called, The LORD our righteousness."