2.8 Include Internal Symbols: -L

Symbols beginning with system-specific local label prefixes, typically ‘.L’ for ELF systems or ‘L’ for traditional a.out systems, are called internal symbols. See Symbol Names. Normally you do not see such symbols when debugging, because they are intended for the use of programs (like compilers) that compose assembler programs, not for your notice. Normally both as and ld discard such symbols, so you do not normally debug with them.

This option tells as to retain those internal symbols in the object file. Usually if you do this you also tell the linker ld to preserve those symbols.