"destitute, poverty-stricken," early 14c., penyles, from penny + -less.

1833, "penniless," from cash (n.) + -less. Of financial transactions, "done without paper money or specie," 1947.

mid-15c., "make clean," from clean (adj.). Related: Cleaned; cleaning. From clean out "clean by emptying" comes sense of "to leave bare" (1844); cleaned-out "left penniless by losses" is from 1812.