Etymology
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infinitesimal (adj.)
1710 (1650s as a noun), "infinitely small, less than any assignable quantity," from Modern Latin infinitesimus, from Latin infinitus "infinite" (see infinite) + ordinal word-forming element -esimus, as in centesimus "hundredth." Related: Infinitesimally.
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differential (adj.)
Origin and meaning of differential

1640s, "making or exhibiting a difference," from Medieval Latin differentialis, from Latin differentia "diversity, difference" (see difference). Related: Differentially. As a noun in mathematics, "an infinitesimal difference between two values of variable quantity," from 1704. Differential calculus is attested from 1702.

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overlord (n.)

late 12c., "a feudal superior, ruler possessing the fealty of other rulers," from over- + lord (n.). In English history, especially a king of one of the Anglo-Saxon realms who held pre-eminence or authority over some of the other kings and chiefs. The word was chosen in 1943 as the Allied code-word for the invasion of western Europe that resulted in D-Day.

 In the perspective of 'Overlord,' that one huge hazardous offensive operation on which, it seemed, the fate of the world depended, smaller adventures receded to infinitesimal importance. [Evelyn Waugh, "Unconditional Surrender"]
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