3 letters · 5 points in Scrabble
originRepresenting oh pronounced with the mouth snapped closed at the end (IPA⁽ᵏᵉʸ⁾: /oʊp/, [oʊp̚]) (excrescent /p/). Compare yep, yup, nope, and welp.
Etymology from Wiktionary, CC BY-SA 3.0