The Collaborative International Dictionary of English v.0.48:
Peg \Peg\ (p[e^]g), n. [OE. pegge; cf. Sw. pigg, Dan. pig a
point, prickle, and E. peak.]
1. A small, pointed piece of wood, used in fastening boards
together, in attaching the soles of boots or shoes, etc.;
as, a shoe peg.
2. A wooden pin, or nail, on which to hang things, as coats,
etc. Hence, colloquially and figuratively: A support; a
reason; a pretext; as, a peg to hang a claim upon.
3. One of the pins of a musical instrument, on which the
strings are strained. --Shak.
4. One of the pins used for marking points on a cribbage
5. A step; a degree; esp. in the slang phrase "To take one
down a peg."
To screw papal authority to the highest peg.
And took your grandees down a peg. --Hudibras.
6. A drink of spirits, usually whisky or brandy diluted with
soda water. [India]
This over, the club will be visited for a "peg,"
Anglice drink. --Harper's
[Webster 1913 Suppl.]
7. (Baseball) a hard throw, especially one made to put out a
baserunner; as, the peg to the plate went wild.
peg board, a board with multiple small holes into which
pegs can be inserted in different arrays so as to form
hooks from which to hang tools or other objects for
convenient access; it is typically hung from a wall in a
Peg ladder, a ladder with but one standard, into which
cross pieces are inserted.
Peg tankard, an ancient tankard marked with pegs, so as
divide the liquor into equal portions. "Drink down to your
Peg tooth. See Fleam tooth under Fleam.
Peg top, a boy's top which is spun by throwing it.
Screw peg, a small screw without a head, for fastening
[1913 Webster +PJC]