Slakoth is a brown, quadrupedal Pokémon with sloth-like qualities. It has coarse, shaggy fur with two dark brown stripes on its back. There is a scruff of fur on top of its head, and it has a large, pig-like pink nose, pink eyelids, and dark rings around its eyes. It has long, lanky arms, but shorter legs. Each paw has two sharp claws, and there are pink paw pads on the back feet. Its underbelly and rear are also pink.
Slakoth lolls around and sleeps for more than twenty hours a day, which can make those around it drowsy. Since it does not move very much, it does not need much food and only eats three leaves each day. Its heart only beats once a minute. In Generation III, Slack Off was its signature move. It makes its nest in tropical forests, and keeps the same one during its entire life. However, it can travel far by swimming in rivers.
According to Ken Sugimori in an interview, Slakoth's name was conceived first before its character design was created.
Slakoth is based on sloths, perhaps specifically the two-toed sloth. It also has some similarities to human infants, such as spending more time sleeping than awake, and primarily lying on its stomach, as babies do not have the muscle mass to hold themselves upright.
Slakoth's evolutionary line goes through three stages of energy, where Slakoth is lazy, Vigoroth becomes extraordinarily energetic, and later Slaking becomes lazy again. This may be a reference to the Sphinx's riddle, in which the baby crawls on four legs, the adult has the most energy and walks on two legs, and the old man walks on three legs, one of which is a cane. In the case of Slaking, two legs and an arm touch the ground in its most preferable position.
Slakoth may be a combination of slack off and sloth.
Namakero may be a combination of 怠ける namakeru (to slack off/laze around) and 樹懶 namakemono (sloth).