early 15c., "benefit, profit, welfare;" also "a convenient or useful product," from Old French commodit "benefit, profit" (15c.) and directly from Latin commoditatem (nominative commoditas) "fitness, adaptation, convenience, advantage," from commodus "proper, fit, appropriate, convenient, satisfactory," from com-, here perhaps an intensive prefix (see com-), + modus "measure, manner" (from PIE root *med- "take appropriate measures").
From early 15c. as "article of merchandise, anything movable of value that can be bought or sold." General sense "property, possession" is from c. 1500.