Here’s a great quote from an online Lisp book that I was browsing through today
(the very last sentence cracks me up :) )

Lisp finesses the memory leakage problem by never allowing the programmer
to release unused memory. The idea here is that the computer can determine
when a block of memory is unreachable with complete accuracy. This
unreachable block is said to be garbage because it is no longer useful to any
part of the program. The garbage collector runs automatically to gather all
these unused blocks of memory and prepare them for reuse. The algorithms
that do this are very tricky, but they come built into your Lisp system.

Historically, garbage collection has been slow. The earliest garbage collectors
could literally lock up a system for hours. Performance was so poor that early
Lisp programmers would run with garbage collection turned off until they
completely ran out of memory, then start the garbage collection manually and
go home for the rest of the day.