lallaloosa

Also from H.L. Mencken’s ‘The American Language’ (1921):

“The immigrants from the South of Ireland, during the period under review, exerted an influence upon the language that was vastly greater than that of the Germans, both directly and indirectly, but their contributions to the actual vocabulary were probably less. They gave American, indeed, relatively few new words; perhaps shillelah, colleen, spalpeen, smithereens and poteen exhaust the unmistakably Gaelic list. Lallapalooza is also probably an Irish loan-word, though it is not Gaelic. It apparently comes from allay-foozee, a Mayo provincialism, signifying a sturdy fellow. Allay-foozee, in its turn, comes from the French allez-fusil, meaning “Forward the muskets!”—a memory, according to P. W. Joyce, of the French landing at Killala in 1798.”

http://www.bartleby.com/185/16.html