I know the meaning, but don't know how or where it originated
2 Answers
According to the Farlex Partner Idioms Dictionary the expression:
no better than you should (or ought to) be - regarded as sexually promiscuous or of doubtful moral character.
This phrase dates back to the early 17th century. Used typically of a woman, it is now rather dated.
Randle Cotgrave compiled and published A Dictionarie of the French and English Tongues in 1611, which included
Putte: f. A wench, laſſe, girle, modder; (eſpecially one that is no better than ſhe ſhould be.)
so the phrase is presumably older than that. The word, with the same meaning of sexual promiscuity, is written "pute" in modern French.