ETYMOLOGY
a reduplicated term, of which the elements are unknown;
from the mid 16th century – in the singular, originally denoted a knickknack or small article
EXAMPLE (for n. 1)
“… Andy Collins, an Irishman, who has lived alone in his cabin, about a mile below us, for a year or more, has been a hard drinker ever since we have known him. He bought his rum by the gallon and kept soaked all the time. Tuesday night he had a bad attack of the jim-jams, and his nearest neighbor, O’Neil, heard him yelling and shrieking like all possessed. …”
From: The Diary of a Forty-Niner
By Chauncey Canfield, 1906
Chapter XVI, February 1, 1852
Lexicophilia 