If you search for victorian maids in images, they don't seem to all be doing that gesture. On paintings of (hand)maidens, most of the time their hands are handling objects. Is that a specific pose or is that behavior? So I wondered specifically if maids - or women of a certain era - were taught to act in such a way or would they be generally so familiar with singing techniques as to spontaneously do a recitation handsclap in a - tenseful - way in different contexts. Consider these images:
Coronation of the Queen of England, Elizabeth II, 1953
I don't think there's any randomness here; this is an incredible show of power. Were the hand placement random it wouldn't be so twice on the same occasion. And the right hand overtaking the left comes as no surprise. This is I think a display of classic (British) etiquette. It also showcases an intuitive yet thorough understanding of the lexical, symbolic and cultural underpinnings associated with the (word) hand.
The NED provides insight: 3. In reference to action performed with the hand and hence (fig.) to action generally; thus often=agency, instrumentality[...]. - 5. As used in various ways of making a promise or oath; (spec.)[...] marriage. - 6. Hence, In oaths[...]. - 8. A person employed by any other in manual work. - 10. [...]a person[...] as the source from which something is obtained[...]+references to trust and best price. - 12. Horsemanship. - 20. A lineal measure. Usage of clean hands: freedom from wrongdoing, innocence and uprightedness of life. Of course there's come to hand, give one's hand etc. to no end. Considering the hand/arm are also heraldic symbols, and looking briefly at the countless religious references associated with cross, it's unlikely such a gesture is an attempt at crossing hands or fingers, especially not while mixing random colors.
The right hand
I think it's also easy to identify that historically in the Western world the left hand was always considered suspicious or "sinister" and treated very differently from the "right" hand(see right-handed, i.e. of the right kind). Within that frame of thought if one had to be shown it should be the right hand.
The grace of repose
And the end of the 19th "Victorian" sort of etiquette. Such as holding a fork with the right hand and having the Routledge tell you how to carve(lobster would have been useful) or that [w]ashing your hands in milk and water, for 2-3 days, will make them white. There is great care for "the unity of the hands". In a document I found the following:
The nervous toying with ear-rings or brooches, or dress buttons, is
another mannerism to be guarded against. The hands should learn the
grace of repose. It is a great triumph of nervous control[...]
It's about acting in a composed manner, showing composure. Surely the hands take part in a graceful composition.
A. Therefore I think this is about a display of honest, serving, dextrous hands, and what composed/mannered used to mean in the Victorian era, which may seem like mannerism today.