the.com/cell membrane

means The thin, flexible layer surrounding a cell that holds its contents together and controls what passes in and out.

from The 'cell' part traces to a 17th-century scientist who viewed cork under a microscope and saw tiny boxes resembling the small rooms, or 'cellae,' that monks lived in — from Latin cella. 'Membrane' comes from Latin membrana, meaning skin or parchment, itself related to membrum (limb or body part), since thin animal skins were once stretched and used as writing surfaces. Put together, the term literally means 'the skin of the little room' — which is a fairly accurate description of a structure made of fatty molecules that wraps each cell like taut parchment.