1640s, "civil and gracious, desiring to please;" 1670s, "disposed to comply with another's wishes;" from French complaisant "pleasing, obliging, gracious" (16c.), present participle of complaire "acquiesce to please," from Latin complacere "be very pleasing to" (see complacent, its doublet, with which it overlapped in sense until mid-19c.). The French spelling possibly was influenced by Old French plaire "gratify." Related: Complaisantly.
