Am 25.10.2018 um 16:04 schrieb
I do not see a possibility
to check names provided the order above

Yes, I know. Right now I was only picking up the point of whether built-in function names should be "especially" protected.

The possible clash between series names and user-written functions (from packages or ad hoc) when it comes to taking lags (or leads) via the round-bracket syntax is the other ongoing topic.