Etymology
Advertisement
infest (v.)
late 15c., "to attack, assail, hurt, distress, annoy," from Old French infester (14c.), from Latin infestare "to attack, disturb, trouble," from infestus "unsafe, hostile, threatening, dangerous," originally "inexorable, not able to be handled," from in- "not, opposite of" (see in- (1)) + -festus, perhaps "(able to be) seized" (see manifest (adj.)). Sense of "swarm over in large numbers, attack parasitically" first recorded c. 1600. Related: Infested; infesting.
Related entries & more 
Advertisement
infestation (n.)
early 15c., "a being infested," from Old French infestacion, from Late Latin infestationem (nominative infestatio) "a troubling, a disturbing, a molesting," noun of action from past participle stem of Latin infestare "to attack, disturb" (see infest).
Related entries & more 
manifest (adj.)
Origin and meaning of manifest

late 14c., "clearly revealed to the eye or the understanding, open to view or comprehension," from Old French manifest "evident, palpable," (12c.), or directly from Latin manifestus "plainly apprehensible, clear, apparent, evident;" of offenses, "proved by direct evidence;" of offenders, "caught in the act," probably from manus "hand" (from PIE root *man- (2) "hand") + -festus, which apparently is identical to the second element of infest.

De Vaan writes, "If manifestus may be interpreted as 'caught by hand', the meanings seem to point to 'grabbing' or 'attacking' for -festus." But he finds none of the proposed ulterior connections compelling, and concludes that, regarding infestus and manifestus, "maybe the two must be separated." If not, the sense development might be from "caught by hand" to "in hand, palpable." 

Manifest destiny, "that which clearly appears destined to come to pass; a future state, condition, or event which can be foreseen with certainty, or is regarded as inevitable" was much used in American politics from about the time of the Mexican War "by those who believed that the United States were destined in time to occupy the entire continent" [Century Dictionary].

Other nations have tried to check ... the fulfillment of our manifest destiny to overspread the Continent allotted by Providence for the free development of our yearly multiplying millions. [John O'Sullivan (1813-1895), "U.S. Magazine & Democratic Review," July 1845]

The phrase apparently is O'Sullivan's coinage; the notion is as old as the republic.

Related entries & more 
parasitize (v.)

in zoology, "infest as a parasite," 1880, from parasite + -ize. Related: Parasitized; parasitizing.

Related entries & more 
plague (v.)

late 15c. (Caxton), "infest with disease or other natural calamity," from Middle Dutch plaghen, from plaghe (n.) "plague" (see plague (n.)). The sense of "vex, harass, bother, annoy" is recorded from 1590s. Related: Plagued; plaguing.

Related entries & more 
Advertisement