From the Super Mario Wiki
A Noko Bombette is a small turtle with a bomb for a shell found in Super Mario Land 2: 6 Golden Coins. Mario must try to avoid them, though they mostly appear in tight corridors, making this a difficult task. It is one of the few enemies that cannot be defeated by a Fireball. Instead, they must be jumped upon. However, unless a Spin Jump is used, the attack will cause the Noko Bombette to explode a few seconds after the jump. If Mario is caught in the blast, he will take damage.
Noko Bombette is the spiritual successor of the Nokobon enemies of Super Mario Land (later renamed to Bombshell Koopa), with both even being described verbatim as "a turtle with a bomb on its back" in their respective game manuals. However, while Nokobons are Koopas with bombs for shells, Noko Bombettes more closely resemble Buzzy Beetles, and share their immunity to fireball attacks. Their Japanese name, Nokobon Metto is even a combination of the other two enemies' names (Metto being Buzzy Beetle's name in Japan, while Nokobon was the same in both languages until the English rename).
Names in other languages
|"Nokobon" was the original name of Bombshell Koopas of Super Mario Land; it comes from Koopa Troopa's Japanese name 「ノコノコ」 Nokonoko, with bon coming from the English "bomb". 「メット」 Metto is the Japanese name for Buzzy Beetle and means "helmet".