These are all Indo-European languages. But interestingly, this has been transported even to Finnic languages, which are grammatically entirely different and unr

These are all Indo-European languages. But interestingly, this has been transported even to Finnic languages, which are grammatically entirely different and unrelated, but still have plural forms for the same words: pants -> Finnish "housut", scissors -> "sakset"; there is no singular "housu" or "saksi" in that meaning. As above, there is the singular "saksi" but it means a Saxon.