Why is RAISERROR misspelled? Or is it not?

Question

Why isn\'t RAISERROR spelled RAISEERROR? Where is the second E? I could understand if it were some ancient keyword length constraint, but I would

Answer 1

From Getting feedback / progress from batches and stored procedures by Jens K. Suessmeyer:

Ever asked yourself why there is only one "e" in Raiserror? That is from the old Sybase days where two [of the same] same character were cut back to only [one]