early 15c., "viscous, sticky; slimy and ropy," from Medieval Latin muscilaginosus, from Late Latin mucilaginosus, from mucilago (see mucilage). Related: Mucilaginously; mucilaginousness.
late 14c., mussillage, "viscous substance found in vegetable material," from Old French mucilage (14c.) and directly from Late Latin mucilago "musty or moldy juice" (4c.), from Latin mucere "be musty or moldy," from mucus "mucus" (see mucus). Meaning "adhesive gum" is attested by 1859.