Lint was a program for K&R (pre-ANSI-C?) C source code which discovered ``lint''---literally bits of fluff in the code. Lint was necessary because prior to ANSI-C? the C language was much looser about what it accepted, arguments and variables could have implicit types and there were a range of other conveniences. Lint performed source code checking in an era when compilers didn't. With modern Compilers, lint's function is performed by simply compiling with all the warning flags turned on (i.e. gcc -Wall ...).
The name Lint lives on in xmllint(1) and other checkers and validators.
