(Looks up a couple of entries)
Perhaps Clam up?
But to be serious for a moment, The P.I.V. says [ klam/i (intr) Plurvoĉe krii. ] And that's all it says. But you were actually, apparently, asking for the etymology of reklami, or at least, I can give you that and klami simultaneously.
From "La konciza etimologia vortaro" Fare de André CHERPILLOD: reklami L. rĕclamare <- re~ «re~» + clamare «klami» <= H.E. kel «krii». So both the root words are derived from the Latin, but the klam/i part is traceable back to the ancient Hindo-European proto-languages.
I hope that this is satisfactory. Mi nun enlitiĝos, kaj dormos kiel klamo.
I put "Who advertised the festivity?" and it was marked incorrect. Duolingo said I should have put "Who advertised the festival?" I checked in 2 dictionaries, and both have "Festo" as the Esperanto for "festivity", and "festivalo" for "festival".