1540s, "to plant in" (abstractly, of ideas, emotions, etc.), from French implanter "to insert, engraft" (alongside Old French emplanter "to plant"), literally "plant in," from assimilated form of in- "into, in, on, upon" (from PIE root *en "in") + planter "to plant" (see plant (n.)). Meaning "surgically implant (something) in the body" is from 1886, originally of teeth. Implanted is attested earlier, from early 15c., probably based on Medieval Latin implantus. Related: Implanting.
also *pletə-, Proto-Indo-European root meaning "to spread;" extension of root *pele- (2) "flat; to spread."
It forms all or part of: clan; flan; flat (adj.) "without curvature or projection;" flat (n.) "a story of a house;" flatter (v.); flounder (n.) "flatfish;" implant; piazza; place; plaice; plane; (n.4) type of tree; plant; plantain (n.2); plantar; plantation; plantigrade; plat; plate; plateau; platen; platform; platinum; platitude; Platonic; Plattdeutsch; platter; platypus; plaza; supplant; transplant.
It is the hypothetical source of/evidence for its existence is provided by: Sanskrit prathati "spreads out;" Hittite palhi "broad;" Greek platys "broad, flat;" Latin planta "sole of the foot;" Lithuanian platus "broad;" German Fladen "flat cake;" Old Norse flatr "flat;" Old English flet "floor, dwelling;" Old Irish lethan "broad."
"to set in, put or place in," 1520s, from Latin insertus, past participle of inserere "to graft, implant," from in- "in" (from PIE root *en "in") + serere "join together, arrange, put in a row," from PIE root *ser- (2) "to line up." Middle English had inseren "to set in place, to graft, to introduce (into the mind)" (late 14c.), directly from the Latin verb. Related: Inserted; inserting.
From late 14c. as "to dwell, live; to have temporary accommodations; to provide (someone) with sleeping quarters; to get lodgings." Sense of "plant, implant, get (a spear, bullet, fist, etc.) in the intended place, to make something stick" is from 1610s. Meaning "deposit" (a complaint, etc.) with an official" is from 1708. Related: Lodged; lodging.