Ways and Means comes from a committee of the House of Commons which used to sit to consider the 'ways and means' or taxation needed to raise revenue for the Government.
The Chairman of Ways and Means is the principal Deputy Speaker. In addition he or she is always chairman of any Committee of the whole House, and has general oversight of matters connected with private bills. The Chairman of Ways and Means usually occupies the chair when budget statements are made or finance bills discussed.
Further information on this subject can be found from the following links.