  In the paper we make an effort to answer the question ``What if Arzel\`a and
Ascoli lived long enough to see Pego theorem?''. Giulio Ascoli and Cesare
Arzel\`a died in 1896 and 1912, respectively, so they could not appreciate the
characterization of compact families in $L^2(\mathbb{R}^N)$ provided by Robert
L. Pego in 1985. Unlike the Italian mathematicians, Pego employed various tools
from harmonic analysis in his work (for instance the Fourier transform or the
Hausdorff-Young inequality). Our article is meant to serve as a bridge between
Arzel\`a-Ascoli theorem and Pego theorem (for $L^1(G)$ rather than $L^2(G)$,
$G$ being a locally compact abelian group). In a sense, the former is the
``raison d'\^etre'' of the latter, as we shall painstakingly demonstrate.
