Possible Clues:

• When tripled, et cetera
• One-third of a verbal ellipsis
• When repeated twice, "and so on"
• Third of a Seinfeld line
• When said three times, 'and so on'
• When tripled, ''et cetera''
• Part of a 'Seinfeld' catchphrase
• When tripled, "You get the picture"
• When repeated twice, "et cetera"
• 'Et cetera,' when tripled