How can we know the original meaning of a word with certainty?

In a lot of discussions here in B.S.E, the topic of the exact meaning of some terms keeps recurring, and nobody seems to have the last word. Words such as 'upapajjati', 'paccājāyati', 'abhinibbatti' are often translated as "rebirth", but for some, that doesn't seem to be the case. Or other terms as 'deva' or 'abhiñña' are understood as "god" and "psychic powers", respectively. Or even outside of Buddhist culture we find some terms such as 'prana', 'chakra', 'messiah', and so on. How can we now the way people contemporary to the origin of such words understood those terms? It is possible that they used those words to describe phenomena that we currently know by other more scientific terms? For instance, in this entry (https://torvol.wordpress.com/2017/11/27/the-chakra-system-is-an-analogy-to-get-your-shit-together-not-spiritual-woo-woo/) , this blogger assures that 'chakras' were the way used to talk about the regulation of emotions. I hope you can understand my point. Have a nice day, and thanks for your time!