There are quite a few tools which will suggest which are the most relevant search terms for your website. I find a good starting point to be Google’s own, free Search Console: if you look at the impressions and ignore the clicks, it’ll give you some interesting ideas about what people are searching for, even where your site’s own performance is rubbish. But what most of these tools have in common is that they work around the terms which you already use. They’re not bright enough to tell you that a section of the market refers to a product using a completely different term. If some people refer to blue widgets as red sprockets, but that term doesn’t appear anywhere on your website, you’re unlikely to have appeared in the Google results for that search. So no matter how far down the Search Console list you look, you won’t find red sprockets.
Any of us who’ve been involved in a sector for any length of time will not find these terms a surprise, but we may overlook them. How do we find out (or remind ourselves) what these alternative terminologies are? A really thorough look at competitor websites is in order here. If there is another way of referring to a product, another supplier, somewhere, will use that. Put that term into Google and see what else comes up. It can be an intriguing detective trail which unearths some surprising results. The challenge then is to work that into your own site without making it look too odd.