About Finnish grammer ‘wc:ssä’

I know that ‘in the toilet’ can be expressed as ‘vessassa’, but Google translates it as ‘wc:ssä’. I searched for ‘wc:ssä’ on the Internet and some people did use it in this way, so the grammar is correct. I wonder why there is a colon in the middle of the word? Is this some Finnish grammar?

by Aww_Again