slip of the lip

Idioms and Phrases

Also, slip of the tongue or pen . An inadvertent mistake in speaking (or writing), as in It was just a slip of the lip that made me say the wrong name , or She didn't mean it; it was a slip of the tongue , or He intended to write “the honorable” but a slip of the pen turned it into “reverend.” The usage with pen dates from the mid-1600s; the others are a century or so younger.