"to emit soft, rapid sounds," late 14c. (implied in rustling), of uncertain origin, perhaps imitative (cf. M.L.G. ruschen, M.Du. ruusscen, Ger. rauschen "to rustle"). The noun is attested from 1759. Meaning "steal" (especially cattle) first attested 1882, probably from earlier Amer.Eng. slang sense of "move about vigorously" (1872), perhaps a separate word, compounded from rush and hustle.
(also rustle one's bustle) To bestir oneself; GET OFF one's ASS (1882+)
(also rustle up) To find and produce: where I knew I could rustle up the Lompoc phone book(1844+)
[origin unknown; perhaps fr rush plus hustle]
The Dictionary of American Slang, Fourth Edition by Barbara Ann Kipfer, PhD. and Robert L. Chapman, Ph.D. Copyright (C) 2007 by HarperCollins Publishers. Cite This Source
Idioms and Phrases with rustle up
Get together food or some other needed item with some effort, as in I don't know what we have but I'll rustle up a meal somehow, or You boys need to rustle up some wood for a campfire. The verb rustle here means “to assemble in a hurry.”
[ Late 1800s