UNVEILED:Adrian Peterson Has Another Secret Child! .

Adrian Peterson fathered a 4th child -- his
2nd secret child -- and the mother was a
waitress at a popular Minnesota nightclub,Tmz has learned.

We've confirmed...the
child is a 3-month-old little girl who's living
with her mom in Minnesota.

Sources close to the situation tell us the child's last name
on her birth certificate is listed as
"Peterson."On the day Peterson's 2-year-
old son Ty passed away, the mother of AP's
4th child posted an emotional message on
her Facebook page about the
situation.

"Today has been a long day
finding out my [daughter's] brother passed
away and knowing that she never even got
to meet him.

"Sources connected to the
situation tell us ... the mother of AP's 4th
child first met the NFL star while serving
him as a VIP waitress at a place called
Seven -- a steakhouse, sushi joint and
ultralounge all wrapped in one.

It's unclear
how involved Adrian has been in the child's
life -- but the mother recently posted a
photo showing the child decked out in
Minnesota Vikings gear, so we're guessing
they're cool. Peterson has fathered 3 other
children -- a 6-year-old daughter, a 2-year-
old son and another son, who died just
months after AP learned he was the
father. We called AP & the child's mother
for comment -- so far, no word back.

Says Tmz.