"solid, weighty, compacted into or consisting of a mass," late 14c., from mass (n.1) + -y (2). Related: Massiness.
Entries linking to massy
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.
-y 2
adjective suffix, "full of or characterized by," from Old English -ig, from Proto-Germanic *-iga- (source also of Dutch, Danish, German -ig, Gothic -egs), from PIE -(i)ko-, adjectival suffix, cognate with elements in Greek -ikos, Latin -icus (see -ic). Originally added to nouns in Old English; used from 13c. with verbs, and by 15c. even with other adjectives (for example crispy). Adjectives such as hugy, vasty are artificial words that exist for the sake of poetical metrics.