it

它 is a pictograph of a snake, originally meaning snake. This meaning was later taken over by 蛇. As snakes lack limbs, they are less familiar to humans compared to other creatures, so 它 is used as a third-person pronoun for non-human creatures or inanimate objects. Additionally, both 它 and 虫 are derived from the pictograph of a snake. As both characters later took on other meanings, 蛇 was created to specifically refer to the snake as a creature.