"corruption, rottenness, putrid matter," 1630s, from Medieval Latin putriditas, from Latin putridus (see putrid). In this sense Middle English had putrede (c. 1400).
word-forming element denoting "something made," from Greek plastos "formed, molded," verbal adjective from plassein "to mold" (see plasma). Used to form names of small particles of living matter.
1844, "to act as an optimist, take the most hopeful view of a matter," a back-formation from optimist. Meaning "to make the most of, develop to the utmost" is attested by 1857. Related: Optimized; optimizing.
mid-13c., muk, "animal or human excrement; cow dung and vegetable matter spread as manure," from a Scandinavian source such as Old Norse myki, mykr "cow dung," Danish møg; from Proto-Germanic *muk-, *meuk- "soft," which is perhaps related to Old English meox "dung, filth" (see mash (n.)). Meaning "unclean matter generally" is from c. 1300; that of "wet, slimy mess" is by 1766. Muck-sweat "profuse sweat" is attested from 1690s.