It actually started from "Kosher lines", special subscriptions provided by MNO, with intentionally limited service (blacklisting phone numbers for calls and text, as well as blacklisting websites).
Once teenagers started buying their own subscriptions, it was decided to move the blacklisting into the HW - hence the kosher phones.
Fun fact: since the Jewish orthodox community is relatively poor, yet a strong "buying force" due to their big number, they were able to negotiate very low rates with the MNOs. To prevent secular people from taking advantage of these rates, the Kosher Lines include big fines if used for incoming/outgoing call on Sabath...
For more info: the translated page from Wikipedoa - https://translate.google.com/translate?sl=auto&tl=en&u=https...