There are many words that are often used in place of other words, that are not actually synonymous.
- Disinterested & Uninterested
- Ask(ed) & Axe(d)
- Literally & Figuratively*
Sometimes this is because the words are similar, sometimes it's born out of hyperbole or irony (eg good & bad), sometimes their are totally obscure reasons this happens. Regardless, it is common enough that I would expect it to have a term. Unfortunately trying to google for such a term, because of the way the keywords are used, returns Interminable** results with nothing pertinent within a reasonable depth.
For the record, if an appropriate term does not already exist, I'd like to coin the term pseudosynonym.
*yes, I know technically this is resolved by adding the informal definition to the dictionary.
**yes, I see what I did there, no it was not intentional.