And since we're talking trademark trivia here, be advised that heroin, zipper, aspirin, escalator, granola, yo-yo and linoleum had heydays once upon a time as proper nouns, replete with capital letters and the distinction due singular entities.

Today, all have become common nouns, bereft of monetary value, victims of "genericide". This term was coined by marketing mavens to denote trademarks and brand names repeatedly lower-cased in everyday parlance. Usage demoted them to the humble rank of "generic descriptor."
—Scott Winokur, "The name of the game is the name," The San Francisco Examiner, February 21, 1995

On Feb. 22, 1983, by refusing to grant certiorari, the Supreme Court let stand a decision of the 9th Circuit Court of Appeals that invalidated the trademark registration of the term "MONOPOLY" for Parker Brothers' ever-popular real estate board game. The 9th Circuit declared that the term "MONOPOLY" had become generic, i.e. had become a common descriptive name for that type of board game and thus no longer afforded trademark rights to Parker Brothers, the owner of the "MONOPOLY" trademark registration. ...

The "Monopoly" case presents several difficult issues concerning "genericide" of a trademark — the deterioration of a once valid, protectible trademark into a common term available for use by anyone. Of major concern is the 9th Circuit's use of a novel test emphasizing purchaser motivation to determine the genericness of the "MONOPOLY" mark. According to the 9th Circuit, the genericness of a once-established trademark depends not on any perception that the public may have concerning the jeopardized mark, but rather on what motivates a significant portion of the product's purchasers to buy the trademarked product: a desire to have the product or purchaser loyalty to a known producer. Source-loyalty motivation may be the requirement for mark validity if the 9th Circuit's motivation test becomes the standard.
—Saul Lefkowitz and Barry W. Graham, "Court Rules that 'Monopoly' Has Suffered Genericide," Legal Times, March 7, 1983