What is the X in X-mas?
In music, the speed at which a piece is performed. It is the Italian word for “time.”
A programming language with simple syntax and semantics designed for teaching semantic and pragmatic aspects of programming languages.
["TEMPO: A Unified Treatment of Binding Time and Parameter Passing Concepts in Programming Languages", N.D. Jones et al, LNCS 66, Springer 1978].
The original code name for Mac OS version 8.