“to leave / last (year)” in Japanese is 去, read kyo, ko, sa (きょ, こ, さ). It is a Grade 3 Kyōiku kanji, taught in year 3 of Japanese elementary school, and appears in words such as 去年 (last year).
What does 去 mean?
去年は楽しかった。
Same sound, different character — the classic trap. Compare them side by side: