Green’s Dictionary of Slang

-eroonie sfx

also -amaroot, -arooney, -arootie, -arooty, -ereenie, -eroon, -erooney, -orooney, -orooni, -oroonie
[var. on -erino sfx]

[1910s+] (US) an intensifier, usu. positive and added to various words, e.g. smackeroonie.