8 letters · 13 points in Scrabble
noun a flat (usually rectangular) container for a letter, thin package, etc.
noun any wrapper or covering
noun a curve that is tangent to each of a family of curves
originPIE word *h₁én From French enveloppe. The engineering sense is derived from flight envelope. The verb is from the noun.
Etymology from Wiktionary, CC BY-SA 3.0