innuendo

1555–65; < Latin: a hint, literally, by signaling, ablative of innuendum, gerund of innuere to signal, equivalent to in- in-² + nuere to nod

The English word innuendo comes from the Latin verb innuere meaning “to nod, beckon, give a hint, intimate,” a compound of the preposition and prefix in, in- “in, into” and the verb nuere “to nod.” Nuere does not occur in Latin as a simple verb but only in compounds such as abnuere “to deny, refuse” and annuere “to give the nod to, assent to, grant.” The most often seen, but least noticed, occurrence of annuere appears in the phrase from the Aeneid, annuit coeptis “he (Jupiter) assents to the things begun” on the verso of the one-dollar bill, on either side of the Eye of Providence above the thirteen-tiered pyramid.
In Latin innuendo is a gerund, a verbal noun more or less equivalent to verbal nouns ending in -ing in English, as for instance, the noun “reading” in “I like reading,” which is equivalent to the simple infinitive, as in “I like to read.” Latin innuendo is in the ablative singular case (and so to be translated “by __ing”) and means “by hinting, by intimating.” In legal documents in Medieval Latin, innuendo was used as an adverb meaning “to wit, that is to say, i.e.” (its original meaning in English in the 16th century); innuendo introduced a parenthetical explanation of the exact reference of a noun or pronoun, especially in cases of slander or libel in which innuendo introduced clarifying statements about what and who was meant by the libel or slander. By the late 17th century, innuendo in English acquired a noun sense “an indirect and usually derogatory intimation about someone or something.”