The other Markov's inequality
ethanepperly.com
ethanepperly.com
But the Chebyshev polynomials, especially in their recursive definition, are a stroke of genius.
I believe they’re defining “wiggle” as just the slope/rate of change/derivative
Wiggling feels more like a second-derivative thing to me but that's discussed too - Chebyshev polynomials max out the second derivative as well as the first.