Possible Clues:

• "Thx" counterpart
• 'Thx' counterpart
• Abbr. of politeness
• Counterpart of 'thx'
• Letters from a polite texter
• Bit of texting tact
• "i'm begging u"
• Polite online letters
• 'if u would be so kind'
• 'i'm begging u'