nonsense (n.)
"that which is lacking in sense, language or words without meaning or conveying absurd or ridiculous ideas," 1610s, from non- "not" + sense (n.);
If you Know you Know
sense (n.)
late 14c., "meaning, signification, interpretation" (especially of Holy Scripture); c. 1400, "the faculty of perception;" from Old French sens "one of the five senses; meaning; wit, understanding" (12c.) and directly from Latin sensus "perception, feeling, undertaking, meaning," from sentire "perceive, feel, know."