The meaning in terms of a singular object has evolved from the meaning in terms of a kit of objects, e.g. Feuerzeug was originally a flint stone and a fire striker, Nähzeug (sewing kit) and Sportzeug (sports equipment) are still being used in that manner.
However, I admit, that “stuff” to me as a non native English speaker carries more the meaning of Kram (non purpose) than Zeug (with some purpose).
The meaning in terms of a singular object has evolved from the meaning in terms of a kit of objects, e.g. Feuerzeug was originally a flint stone and a fire striker, Nähzeug (sewing kit) and Sportzeug (sports equipment) are still being used in that manner.
However, I admit, that “stuff” to me as a non native English speaker carries more the meaning of Kram (non purpose) than Zeug (with some purpose).