Etymology
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excretion (n.)

c. 1600, "action of excreting;" 1620s, "that which is excreted," from French excrétion (16c.), from Latin excretionem (nominative excretio), noun of action from past-participle stem of excernere "to sift out, separate" (see excrement).

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excretory (adj.)

"pertaining to excretion," 1680s, from excrete + -ory.

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metabolism (n.)

1878 in the physiology sense of "the sum of the chemical changes within the body by which the protoplasm is renewed, changed, or prepared for excretion," from French métabolisme, from Greek metabole "a change," from metaballein "to change," from meta "change" (see meta-) + ballein "to throw" (from PIE root *gwele- "to throw, reach"). The word also has been used in theology, poetics, and entomology.

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perspiration (n.)

1610s, "a breathing through," a sense now obsolete, from French perspiration (1560s), noun of action from perspirer "perspire," from Latin perspirare "blow or breathe constantly," from per "through" (from PIE root *per- (1) "forward," hence "through") + spirare "to breathe, blow" (see spirit (n.)). Applied by 1620s to "excretion of invisible moistures through the skin," hence its later use as a euphemism for "sweat" (1725).

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