O.E. botm, bodan "ground, soil, foundation, lowest part," from P.Gmc. *buthm- (cf. O.Fris. boden "soil," O.N. botn, Du. bodem, O.H.G. bodam, Ger. Boden "ground, earth, soil"), from PIE base *bhu(n)d(h)- (cf. Skt. budhnah, Avestan buna- "bottom," Gk. pythmen "foundation," L. fundus "bottom, piece of land, farm," O.Ir. bond "sole of the foot"). Meaning "posterior of a man" is from 1794; the verb "to reach the bottom of" is from 1808. Bottom dollar "the last dollar one has" is from 1882.
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 bottom out
Reach the lowest level, as in The recession appears to have bottomed out. This verbal use of bottom originated in the late 1800s and, with the addition of out in the mid-1900s, tends to be used mostly in the context of trade and finance.