Is there absolutely any relation between formaldehyde and Mr. Hyde from 'The Strange Case of Dr. Jekyll and Mr. Hyde'? When I break down for-mal-de-hyde, I get for / mal (bad) / de (of) / Hyde (Mr. Hyde). Does it have a meaning like "bad potion of Hyde" or am I just seeing a weird coincidence?

Only just seen this one, sorry.
You are seeing a weird coincidence. The real breakdown is form-aldehyde. Aldehydes are a group of organic chemicals whose name is reckoned to come from AL-cohol DEHYDogenated, and each aldehyde will have an associated alcohol. https://en.wikipedia.org/wiki/Aldehyde Formaldehyde is also called methyl aldehyde, which gives the alcohol. The form- bit comes from the ease with which formaldehyde is oxidised into formic acid - named from the nasty stuff ants use when they get upset with you (and in turn this derives from Latin; there is a word formication - note spelling - which refers to a condition where you feel as if ants are running about on you). https://en.wikipedia.org/wiki/Formic_acid https://en.wikipedia.org/wiki/Formaldehyde
In water solution, formaldehyde is called formalin, which loses Mr Hyde. An interesting example of what is called 'folk etymology'.