Is there any meaning of the character 冲 that allows to translate it as Vessel (or empty vessel)? The section four of 道德经 states: "道沖而用之或不盈" - 冲 is usually translated here as an empty vessel or emptiness of a vessel - but I am not sure what is the basis for such translation.
There is no original meaning of 沖 that means "vessel" or "pour into". "Pour against" as a later extension, maybe...
说文 is pretty clear that 沖 means to "surge up and shake extensively", i.e. to "gush" (of water).
There is also this phrase in pre-Han text: "盈而不沖". "Fill up but not gush".
Supposedly, there are two original versions of the passage in question:
Your quote is already a slightly edited paraphrase. If we are to stay faithful to what is literally written, we may translate:
道沖而用之有弗盈也，潚呵似萬物之宗 ... 湛呵似或存 = The Law gushes and administers whatever is not filled up, a deep reservoir as if the source of all things ... a flood as if something is alive.
Dao is like a teapot that would never be filled, even if you pour everything in the universe into it. (that's how deep Dao is, it can contains everything in the universe and not be filled up)
I would say” If you pour water into a teapot, the teapot will eventually be filled; but we can never fill Dao up, even if we pour everything in the universe into it”
"沖" here means "pour into"
"道沖" here means "pour (everything in the universe) into Dao"
'道' is metaphorized as limitless vessel