means The amount of matter in an object — its resistance to being pushed around and the reason it feels heavy under gravity (also, a large gathered quantity of stuff, or the central Catholic worship service).

from From Latin 'massa,' meaning a lump or kneaded dough — itself borrowed from Greek 'maza,' a barley cake. The image is of stuff pressed together into a heap, which is exactly how the physical sense still feels. The religious 'Mass' takes a completely different road: it comes from the Latin 'missa' in the dismissal phrase 'Ite, missa est' ('Go, it is sent/dismissed') that ended the service — so the worship 'Mass' is named, oddly, for its own goodbye.