Merriam-Webster's Collegiate® Dictionary, 11th Edition
JIGGER
I. noun
Date: 1675
one that jigs or operates a jig, any of several sails, jig 3a,
4. a. a mechanical device usually with a jerky reciprocating motion, a mold or a machine incorporating a revolving mold on which ceramic items (as plates) are formed, gadget , doodad , a measure used in mixing drinks that usually holds 1 to 2 ounces (30 to 60 milliliters),
II. noun
Etymology: perhaps from Wolof jiga insect
Date: 1781
chigger ,
III. verb
Etymology: frequentative of 2jig
Date: 1867
intransitive verb to jerk up and down, transitive verb to alter or rearrange especially by manipulating