The following conversation suggests “String Pointer Break”:
http://www.cpptalk.net/what-strspn-and-strpbrk-stands-for–vt1253.html
Indeed the Microsoft documentation case is StrPBrk and would tend to confirm that split of words:
http://msdn.microsoft.com/en-us/library/bb760010(VS.85).aspx
And finally this confirms it:
http://www.gnu.org/software/libtool/manual/libc/Search-Functions.html
The strpbrk (“string pointer break”) function is related to strcspn, except that it returns a pointer to the first character in string that is a member of the set stopset instead of the length of the initial substring. It returns a null pointer if no such character from stopset is found.