Work my fingers to the bone
This expression is usually used by someone complaining about another's wastefulness and ingratitude. I work my fingers to the bone to pay for you to have a piano and lessons, but you never practise or make any effort.
It can also be used sympathetically: There are some very good parents in Hong Kong who work their fingers to the bone to give their children a good education.
Clearly the idiom comes from manual (with the hands) labour and gives an image of someone working so hard in the field or factory that their skin and flesh is worn away leaving only bone. Fortunately, this is not likely to happen in Hong Kong and the idiom is a bit exaggerated, but if you think of third world sweatshops it becomes heartbreakingly close to the truth.
At the start of the Industrial Revolution in Britain, many people would have suffered such conditions and the idiom brings to mind a famous poem, The Song of the Shirt. Here are the opening lines and pay attention to the woman's fingers:
'With fingers weary and worn,
With eyelids heavy and red,
A woman sat, in unwomanly rags,
Plying her needle and thread,
Stitch, stitch, stitch!
In poverty, hunger, and dirt,
And still with a voice of dolorous [sad] pitch,
She sang the Song of the Shirt.'
Jump on the bandwagon
This takes us back to the late 19th century world of American politics. Mass democracy meant that politicians needed to get their names known and their supporters excited. There was obviously no television for this purpose. Newspapers were very important and common. Even small places might have two or three taking different positions on important matters.
Then there were political parades. When candidates visited there was as much noise and fun as possible to get people out into the streets and involved in the political process. The bandwagon, a big horse-drawn vehicle, carrying the band was an essential part of these parades. Jumping up on the bandwagon was one way of showing your support for a candidate.
The current idiom, however, means more than supporting something; it means going with the majority. If sushi is suddenly popular in Hong Kong and your canteen starts selling it, they are jumping on the bandwagon, joining the trend.
Sometimes the phrase even means changing our view. If we are not too keen on one team that is standing for the Student Association election, but the whole class seems to like its members, we jump on the bandwagon and become supporters of that team. You will also see climb, or get and hop on the bandwagon.