Trump and Trumpery

Reading "Trumpery - A Twitter meme caused lookups to spike" on M-W got me wondering about Trump and Trumpery. I meant about the words itself and not about candidate Donald Trump's qualities.

Trump

a dependable and exemplary person

Trumpery

worthless nonsense

How did they develop such opposing meanings?

The Merriam-Webster pages that you link to actually give the etymologies of the two words (though I don't blame you for missing it; the Merriam-Webster page structure is a bit hard to follow).

According to those pages, trump is an

alteration of ¹triumph

whereas

Trumpery derives from the Middle English trompery and ultimately from the Middle French tromper, meaning "to deceive." […]

so they're actually unrelated, and the similarity of appearance is coincidental.