Which of these words was originally a protected brand name but lost its trademark status because it became a generic term in everyday language?

The fascinating journey of brand names that became so successful they transformed into generic terms in our everyday language - a process linguists call 'genericide.' These products achieved such market dominance that their brand names became synonymous with entire product categories, changing our lexicon forever. Can you identify which of these common terms originated as a protected trademark but lost its status due to becoming too generic in public usage?

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Escalator (originally an Otis Elevator Company trademark)
Dictionary (originally a Merriam-Webster trademark)
Alphabet (originally a Google parent company trademark)
Keyboard (originally an IBM trademark)