Is Tuesday named for a one-handed god?
"to strike sharply," 1719, probably of imitative origin. The noun is from 1737. The word in out of whack (1885) is perhaps the slang meaning "share, just portion" (1785), which may be from the notion of the blow that divides, or the rap of the auctioneer's hammer.
Worthless; stupid; ''wimpish'': You'll have to deal with some really wack peoplenoun
[probably echoic; in second verb sense, the use of whacks, ''any form of force,'' is attested among Chicago gunmen in 1932]
According to arch-hacker James Gosling, to "...modify a program with no idea whatsoever how it works." (See whacker.) It is actually possible to do this in nontrivial circumstances if the change is small and well-defined and you are very good at glarking things from context. As a trivial example, it is relatively easy to change all "stderr" writes to "stdout" writes in a piece of C filter code which remains otherwise mysterious.