onliest adjective Only.
1931 Goodrich Mt Homespun 63 She’s the onliest one I ever did know that could do such as that. 1962 Dykeman Tall Woman 70 If the bullet had strayed a little closer, I might have lost the onliest heart I’ve got! 1974 Fink Bits Mt Speech 18 Hit’s the onliest knife I’ve got n.d. Mtneer Talk = only one. “He’s my onliest son.” 1994 Montgomery Coll. She treated it as if it was the onlist one she had (Cardewell).
I still hear the word onliest on a regular basis in my part of Appalachia. Sometimes I hear it come right out of my mouth when I say things like:
“When I came by the ball field he was the onliest little boy out there. I reckon they changed the day and he didn’t know.”
“That was my onliest pair of flip-flops!! I can’t believe you left them at the lake.”