slip of the lip

Idioms  

1. Also,. 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.

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Example Sentences

"A slip of the lip can sink a ship," replied Carey, "and I don't intend for my ship to sink."

From Time Magazine Archive

The latest slip of the lip occurred during his Sarajevo visit.

From Time Magazine Archive

While he was waiting for someone to answer the bell, he read the faded sticker on the crystal of the door, “A slip of the lip can sink a ship.”

From "A Confederacy of Dunces" by John Kennedy Toole