Back-handed is synonymous with left-handed and so a backhanded compliment is no different than a left-handed compliment. A backhanded or left-handed compliment is a compliment with an insult at the centre.
In the Presbyterian Review published in 1880 and edited by Samuel J. Wilson, James Eells et al, it was reported that:
But other Jewish Rabbis, as Gratz and Friedlander, have since repeated the view of Geiger. Delitzsch proves the preposterous folly of this left-handed compliment to our Lord. Rabbi Hillel, who died about A.D. 10, was, no doubt, the greatest of Jewish Rabbis and Pharisees, even if we deduct from the fabulous traditions about his learning and wisdom.
Thomas Henry (T.H.) Huxley (1825 – 1895) wrote about Scottish philosopher and historian, David Hume in his book “Hume (English Men of Letters Series)” published in 1879.
Ten years later, he cannot even thank Gibbon for his History without the left-handed compliment, that he should never have expected such an excellent work from the pen of an Englishman.
In the Scientific American Journal, Volume 1007, Issue 19 published on November 8, 1862, on page 295, the following was reported:
Left-Handed Compliment – When Mr. Whiteside finished his five hours’ oration on kars, Lord Palmerston replied that the honorable gentleman’s speech was highly creditable to his physical powers.
But the term left-handed has a definition in the sense of questionable or doubtful that dates back to the early 1600s. In 1614, Ranald Oig seized Edinburgh Castle, that led to Thereon Angus Oig, a younger brother of the imprisoned Sir James Macdonald of Islay, to set about recovering the castle “for the king.”
One of his kinsman was a man by the name of Left-handed Coll Keitache. It is said that Ranald Oig escaped by sea, and Thereon Angus Oig retained the castle, offering to restore it to the Bishop of the Isles on conditions. Sir James Macdonald went to Lochaber, Morar, and Knoydart, and then to Sleat to continue his mission. In the end, he fled from the island and Left-handed Coll Keitach found himself employed by his enemies against his former associates, which he did to the best of his abilities.
Historically Speaking 