a while back
At some point in the past. I bought this dress a while back but have never had a chance to wear it.
a while back
Also, a while ago. Some time in the past, as in I ran into Barbara a while back but didn't get her new address, or John wrote me a while ago about his new baby. This term uses a while in the sense of "a short or moderate time," a usage dating from about 1300.