dissertation (n.)youdaoicibaDictYouDict
1610s, "discussion, debate," from Latin dissertationem (nominative dissertatio) "discourse," noun of action from past participle stem of dissertare "debate, argue, examine, harangue," frequentative of disserere "discuss, examine," from dis- "apart" (see dis-) + serere "to arrange words" (see series). Sense of "formal, written treatise" is 1650s.
dissertateyoudaoicibaDictYouDict
"Discourse on a particular subject", Mid 18th century: from Latin dissertat-, from dissertare 'to continue to discuss'.