Its probably read-to-wear vs made-to-order. Made-to-order is where the garment is custom tailored to the person/model and takes a few weeks to make, where as ready-to-wear is already made in standard sizing and already ready to be shipped and worn.
To my understanding, in the French language to say something is "prêt à porter" (directly translated in English to ready-to-wear) is simply how they would imply something is casual.
If not, then they ain't even clothes to me.
Nobody in the world is even clothes to me.