When people browse your website (which probably looks a lot like other websites), they have certain expectations.
They’ll probably expect to see a button in the top right corner. That’s because of Jakob’s Law. Most users spend most of their time on other sites. That’s why they prefer sites that work the same way as all the other sites.
And if that button is used to log in, they’ll expect the word “login”. Even though “client access” means the same, it’s not what people expect. Don’t try to be clever, use the familiar

Use familiarity to your advantage. No need to break your head over UX copy when many websites have already created a certain standard. Sometimes “book a demo”, should just be “book a demo”.
You should also be careful with familiarity, however. Especially when there is none.
When you’re introducing something new(something other websites, don’t tend to have)there are no expectations. Instead, there’s confusion. There’s unknown territory. Guide your visitor. It’s better to use more copy. And it’s crucial to avoid clever copy.
H/T for today’s post to Growth Design’s case study about Clubhouse