biomass n.

word-forming element, especially in scientific compounds, meaning "life, life and," or "biology, biology and," or "biological, of or pertaining to living organisms or their constituents," from Greek bios "one's life, course or way of living, lifetime" (as opposed to zoe "animal life, organic life"), from PIE root *gwei- "to live."

The correct usage is that in biography, but since c. 1800 in modern science it has been extended to mean "organic life," as zoo-, the better choice, is restricted in modern use to animal, as opposed to plant, life. Both are from the same PIE root. Compare biology.

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.