mass (n.1)

late 14c., "irregular shaped lump; body of unshaped, coherent matter," from Old French masse "lump, heap, pile; crowd, large amount; ingot, bar" (11c.), and directly from Latin massa "kneaded dough, lump, that which adheres together like dough," probably from Greek maza "barley cake, lump, mass, ball," which is related to massein "to knead," from PIE root *mag- "to knead, fashion, fit."

The sense in English was extended 1580s to "a large quantity, amount, or number." Meaning "bulk" in general is from c. 1600. As "the bulk or greater part of anything" from 1620s. Strict sense in physics, "quantity of a portion of matter expressed in pounds or grams" is from 1704.

As an adjective, "of, involving, or composed of masses of people; done on a large scale," from 1733, first attested in American English mass meeting "public assembly persons in mass or of all classes to consider or listen to the discussion of some matter of common interest." Mass culture is from 1916 in sociology (earlier in biology); mass hysteria is from 1914; mass movement is from 1897; mass grave is from 1918; mass murder from 1880.

"eucharistic service," Middle English messe, masse, from Old English mæsse, from Vulgar Latin *messa "eucharistic service," literally "dismissal," from Late Latin missa "dismissal," fem. past participle of mittere "to let go, send" (see mission).

Probably so called from the concluding words of the service, Ite, missa est, "Go, (the prayer) has been sent," or "Go, it is the dismissal." The Latin word sometimes was glossed in Old English as sendnes "send-ness." Meaning "musical setting of certain parts of the Catholic (or Anglican) liturgy" is by 1590s.

late 14c., transitive, "to form into a mass" (implied in y-maced), from mass (n.1) or from French masser. Intransitive sense of "to gather in a mass, collect in masses" is by 1560s. Related: Massed; massing.