The literal translation of the term forbidden
is circumcised.
The word is used widely in the Old Testament to define someone who is outside the holy community. It is also used metaphorically of things that are inappropriate, or that do not work correctly (see, for example, Exodus 6:12, Exodus 6:30; Deuteronomy 10:16). Understood in this way, the word means that the fruit is taboo and not to be touched.
23 Quand vous serez entrés dans le pays, et que vous y aurez planté toutes sortes d'arbres fruitiers, vous en regarderez les fruits comme incirconcis; pendant trois ans, ils seront pour vous incirconcis; on n'en mangera point.