Tupperware is a brand name for plastic food storage containers with tight-fitting lids that seal to keep food fresh. The name comes from Earl Tupper, who invented these containers in the 1940s, combined with “ware” (meaning manufactured goods).

What made Tupperware special was its airtight seal. Before Tupperware, people stored leftovers in bowls covered with cloth or wax paper, which let air in and dried food out. Tupperware's flexible lids snapped onto containers with a satisfying burp of air, creating a seal that kept leftovers fresh for days. You could stack them neatly in the refrigerator without spills or smells escaping.

The word has become so common that people often use it generically to mean any plastic food container, even if it's actually a different brand. Your mom might ask you to “put that in some Tupperware” when she really means any reusable plastic container. Just like people say “Kleenex” for any facial tissue or “Band-Aid” for any adhesive bandage, “Tupperware” often means plastic food storage containers in general.