To keep faith; the exact performance of an agreement, as, “To keep touch with my promise” (More). The idea seems to be embodied in the proverb, “Seeing is believing, but feeling is naked truth.”
And trust me on my truth, If thou keep touch with me, My dearest friend, as my own heart, Thou shalt right welcome be.
Songs of the London Prentices, p. 37.
Source: Dictionary of Phrase and Fable, E. Cobham Brewer, 1894