sesquipedalian (n.) Look up sesquipedalian at Dictionary.com
1610s, from Latin sesquipedalia verba "words a foot-and-a-half long," in Horace's "Ars Poetica" (97), nicely illustrating the thing he is criticizing, from sesqui- "half as much again" (see sesquicentennial) + pes "foot" (see foot (n.)).