c. 1600, "subject for investigation" (a sense now obsolete), also "systematic search, formal inquiry into some problem or topic," from Latin disquisitionem (nominative disquisitio) "an inquiry, investigation," noun of action from past-participle stem of disquirere "inquire," from dis- "apart" (see dis-) + quaerere "seek, ask" (see query (n.)). Sense of "a long speech, a formal dissertation" first recorded 1640s. Related: Disquisitional.
