A bow tie was an accessory worn by men on Earth that was fastened around one's neck and adorned the collar of a shirt.
The character Al Goddard from the old Earth movie Appointment with Danger wore a bow tie. (ENT: "Impulse")
Zabo wore a bow tie on the planet Sigma Iotia II. (TOS: "A Piece of the Action")
The historian Whalen wore a bow tie when he accompanied Captain Jean-Luc Picard and Data into the holoprogram of the Dixon Hill series in 2364. Some years later, Picard himself wore a bow tie in the program. (TNG: "The Big Goodbye";Star Trek: First Contact)
The bass player at the Bourbon Street Barn wore a bow tie. (TNG: "11001001")
The Comic wore a bow tie during his comedy act. (TNG: "The Outrageous Okona")
The waiter Henry also wore a bow tie. (DS9: "Badda-Bing, Badda-Bang")