1765, "feminine finery, something used by women purely for adornment," from French chiffon (17c.), diminutive of chiffe "a rag, piece of cloth" (17c.), which is of unknown origin, perhaps a variant of English chip (n.1) or one of its Germanic cousins. Klein suggests Arabic. Meaning "sheer silk fabric, thin gauze" is from 1890. Extension to pastry is attested by 1929, probably on the notion of "lightness."
early 15c., "gentleness, lightness," from Old French facilité "easiness, ease," from Latin facilitatem (nominative facilitas) "easiness, ease, fluency, willingness," from facilis "easy to do," from facere "to do" (from PIE root *dhe- "to set, put"). First in a medical book:
If it be nede forto smyte [the head] wiþ a malle, be it done with esynez or facilite [transl. Guy de Chauliac's "Grande Chirurgie"]
Its sense in English expanded to "opportunity" (1510s), to "aptitude, ease, quality of being easily done" (1530s). Meaning "place for doing something" which makes the word so beloved of journalists and fuzzy writers, first recorded 1872, via notion of "physical means by which (something) can be easily done."
in prosody, a foot of two syllables, the first short or unaccented, the second long or accented, 1842, from French iambe (16c.) or directly from Latin iambus "an iambic foot; an iambic poem," from Greek iambos "metrical foot of one unaccented followed by one accented syllable" (see iambic). Iambus itself was used in English in this sense from 1580s. In Greek, the measure was said to have been first used by satiric writers.
[The Iambus] is formed constantly by the proper accentuation of familiar, but dignified, conversational language, either in Greek or English : it is the dramatic metre in both, and in English, the Epic also. When the softened or passionate syllables of Italian replace the Latin resoluteness, it enters the measure of Dante, with a peculiar quietness and lightness of accent which distinguish it, there, wholly from the Greek and English Iambus. [Ruskin, "Elements of English Prosody, for use in St. George's Schools," 1880]