Backfriend

They had vvings of goodvvill to fly vvith, but no vvebbes on their feete to ſvvimme vvith, for except the vvaterfoules had mercie vpon them, and ſtood their faithfull confederates and backe-friends, on their backes to tranſport them, they might returne home like good fooles, and gather ſtravves to build their neſts, or fal to theyr old trade of picking vvormes.

Source: wiktionary

Tho they give us neither VVine nor Ale; yet if they give us a Cup of cold VVater in the time of need, in the name of Diſciple, in the name of Miniſters, they ſhall not loſe their Revvard. Novv, vvell's us for our Back-friend, he vvill ay maintain our Cauſe; […]

Source: wiktionary

I would always have been able to keep up my spirits with the reflection, that I had, in case of the worst, a stout back-friend in this uncle of mine. But now I have seen him, and, woe worth him, there has been more help in a mere mechanical stranger than I have found in my own mother's brother, my countryman and a cavalier.

Source: wiktionary

[“H]e said to me, ‘Adelle, I’m going out. I’ve got a backfriend to meet.’” / “A ‘backfriend’?” / “Yes. Evidently he had a late-night appointment with someone at Wabash. That was the way he liked to do it.”

Source: wiktionary