And it will be ever thus, plain Jane, for where could we ever find a man worthy of our splendid selves?
"plain Jane," laughed little Estella, swinging on Jane's arm.
"unattractive woman," first attested 1912.
Unadorned; stark; no-frills:''Plain Jane'' is how one gun collector describes the look
[1912+; the earliest examples read plain Jane and no nonsense]