How does this happen ? The poster above you isn't really Polish ? How can someone that claims to know Polish not know there's two different words ?

And in Russian we use "jad" ("яд" in cyrillic) for both. Although there is the word "отрава", which can be used for poisons and "яд" is closer to "venom" the difference is almost non-existant and both are often used interchangeably.