Etymology
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sporting (adj.)
c. 1600, "playful;" 1799 as "characterized by conduct constant with that of a sportsman" (as in sporting chance, 1897), present-participle adjective from sport (v.).
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Planck 

in physics, in reference to the work of German physicist Max Planck (1858-1947); such as Planck's constant, attested in English from 1901.

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stable (adj.)
mid-12c., "trustworthy, reliable;" mid-13c., "constant, steadfast; virtuous;" from Old French stable, estable "constant, steadfast, unchanging," from Latin stabilis "firm, steadfast, stable, fixed," figuratively "durable, unwavering," literally "able to stand," from PIE *stedhli-, suffixed form of root *sta- "to stand, make or be firm." From c. 1300 as "well-founded, well-established, secure" (of governments, etc.). Physical sense of "secure against falling" is recorded from late 14c.; also "of even temperament." Of nuclear isotopes, from 1904.
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inequable (adj.)
"not uniform, changeable," 1716, from Latin inaequabilis "unequal," from in- "not" (see in- (1)) + aequabilis "similar, equal; constant, not varying" (see equable). Related: Inequability (1580s).
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whirligig (n.)
mid-15c., a child's toy, from whirl (v.) + gig (see gig (n.1)). Meaning "anything in constant motion" is from 1580s; "fickle, flighty person" is from c. 1600; as a type of water beetle, from 1713.
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invariable (adj.)

"constant, uniform, unchanging," early 15c., from Old French invariable (14c.) and directly from Medieval Latin invariabilis, from in- "not, opposite of" (see in- (1)) + variabilis "changeable" (see variable). Related: Invariably.

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perseverant (adj.)

mid-14c. perseveraunt (implied in perseverantly) "constant, steadfast; persistent, unflagging," from Old French persévérant (12c.), present participle of persévérer (see persevere). Marked as obsolete in Century Dictionary (1895). Related: Perseverantly.

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infrequent (adj.)
1530s, "little used" (now obsolete); 1610s, "not occurring often," from Latin infrequentem (nominative infrequens) "occurring seldom, unusual; not crowded, absent," from in- "not" (see in- (1)) + frequens "repeated, regular, constant, often" (see frequent). Related: Infrequently.
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firm (n.)
"business house," 1744, according to Barnhart from German Firma "a business, name of a business," originally "signature," from Italian firma "signature," from firmare "to sign," from Latin firmare "make firm, affirm," in Late Latin, "confirm (by signature)," from firmus "strong; stable," figuratively "constant, trusty" (see firm (adj.)).
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fishbowl (n.)

also fish-bowl, "a glass globe in which fish are kept," 1850, from fish (n.) + bowl (n.). The form goldfish-bowl is attested from 1841. Figuratively, as a place where one is under constant observation, by 1957. Fish-globe is by 1858.

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