Old English beleogan "to deceive by lies," from be- + lie, v.1 "to lie, tell lies." Current sense of "to contradict as a lie" is first recorded 1640s. The other verb lie once also had a formation like this, from Old English belicgan, which meant "to encompass, beleaguer," and in Middle English was a euphemism for "to have sex with" (i.e. "to lie with carnally").