[thwarted]

It's literally in the definition of "butler".

Butler:

1 : a manservant having charge of the wines and liquors. 2 : the chief male servant of a household who has charge of other employees, receives guests, directs the serving of meals, and performs various personal services.

[pfundstein]

I think the distinction is usually drawn at (a) payment is exchanged for services, and (b) the person providing the service is free to leave the role at their discretion (possibly with a contractual requirement to provide advance notice).

[deathlight]

"Will you require buttling today, sir?"

"No, you can go manserve elsewhere for now."