Is it farther or further?
1670s, "oblique hint, indiscreet suggestion," usually a deprecatory one, from Latin innuendo "by meaning, pointing to," literally "giving a nod to," ablative of gerund of innuere "to mean, signify," literally "to nod to," from in- "at" + nuere "to nod" (see numinous). Originally a legal phrase (1560s) from Medieval Latin, with the sense of "to wit." It often introduced the derogatory meaning alleged in libel cases, which influenced its broader meaning. As a verb, from 1706.