1570s, "to purify, clarify, clear from dregs or impurities," from Latin defaecatus, past participle of defaecare "cleanse from dregs, purify," from the phrase de faece "from dregs" (see de- + feces). Figurative sense "purge of extraneous matter" is from 1620s. Excretory sense "void feces from the bowels" is by 1849 in medical writing, probably from French. Related: Defecated; defecating.
