conceit n.

late 13c., conceiven, "take (seed) into the womb, become pregnant," from stem of Old French conceveir (Modern French concevoir), from Latin concipere (past participle conceptus) "to take in and hold; become pregnant" (source also of Spanish concebir, Portuguese concebre, Italian concepere), from con-, here perhaps an intensive prefix (see con-), + combining form of capere "to take" (from PIE root *kap- "to grasp").

Meaning "take into the mind, form a correct notion of" is from mid-14c., that of "form as a general notion in the mind" is from late 14c., figurative senses also found in the Old French and Latin words. Related: Conceived; conceiving.

Nearly all the senses found in Fr. and Eng. were already developed in L., where the primary notion was app. 'to take effectively, take to oneself, take in and hold'. [OED]

"a general notion, the immediate object of a thought," 1550s, from Medieval Latin conceptum "draft, abstract," in classical Latin "(a thing) conceived," from concep-, past-participle stem of concipere "to take in and hold; become pregnant," from con-, here perhaps an intensive prefix (see con-), + combining form of capere "to take" (from PIE root *kap- "to grasp"). In some 16c. cases a refashioning of conceit, perhaps to avoid negative connotations that had begun to cling to that word.