11 letters · 20 points in Scrabble
adjective not easily perturbed or excited or upset; marked by extreme calm and composure
originEtymology tree Proto-Indo-European *né Proto-Indo-European *n̥- Proto-Germanic *un- Proto-West Germanic *un- Old English un- Middle English un- English un- English flap Proto-Indo-European *-tḗr Proto-Indo-European *-dʰlom Proto-Indo-European *-dʰlis Proto-Italic *-ðlis Latin -bilis Latin -ābilis Old French -ablebor. Middle English -able English -able English unflappable From un- + flap (“to…
Etymology from Wiktionary, CC BY-SA 3.0