Is it ensure, insure, or assure?
late 14c., from Old French receptacle (14c.) and directly from Latin receptaculum "place to receive and store things," from receptare, frequentative of recipere "to hold, contain" (see receive). As an adjectival form, receptacular (1847) has been used.
The enlarged upper end of a flower stalk that bears the flower or group of flowers. The fleshy edible part of an apple is actually a modified receptacle. See more at flower.