What does sprintf stand for?

String PRINT Format(ed).

I.e. print to string using a given format.

The various members of the printf family, derived from C where they first appeared (though they hark back to the olden days of BCPL's writef call along that particular lineage), include:

printf    - print formatted (to standard output).
fprintf   - file printf (to a file handle).
sprintf   - string printf (to a string).
snprintf  - sprintf with added overflow protection.

In addition, there are variants of those starting with v (as in vsnprintf) which can take variable arguments like printf itself.

By that I mean that they pass around a varargs argument rather than a series of arguments, allowing you to write your own printf-like function. I've used this before when developing logging libraries in the past.

sprintf originates from C. Refer to e.g.

http://www.cplusplus.com/reference/clibrary/cstdio/sprintf/

where it says:

Writes into the array pointed by str a C string ...

thus: s(tring)printf(ormatted)