What word is on the tip of your tongue but you just can't think of it?

[HungLikeJesus]

What's the word for a brand name used as a generic name? For example, Kleenex for tissue or Jello for gelatin.

[glatt]

a genericized trademark also sometimes known as a proprietary eponym.

Terminology

The terms genericide and genericized trademark are not technical terms. Alternative terms have been suggested by various commentators, such as the judge in Plasticolor Molded Products v. Ford Motor Company, who called genericide a malapropism and suggested genericization or trademarkicide,[13] a member of Cecil Adams's contributing board who suggested brand eponym in The Straight Dope Mailbag,[14] and others who have suggested proprietary eponym. However, to date only genericide has been used in legal literature.[15]