Possible Clues:

• Abbr. sometimes used twice in a row
• And the like: Abbr
• Space-saving letters
• Inclusive abbr
• Yadda, yadda, yadda
• And more: Abbr.
• Letters replacing a list
• "Yada yada yada" letters
• Truncation abbr
• 'Yadda, yadda, yadda'