The Worshipful Master is the principal officer of a Lodge, and is elected to a limited term (as specified in that lodge's bylaws, or that Grand Jurisdiction's constitution) by the Brethren of that Lodge.
The honorary "Worshipful" is used with the following meaing:
wor·ship·ful 2. (initial capital letter) British. a formal title of honor used in announcing or addressing certain highly regarded or respected persons or groups (usually prec. by the).
Some modern day examples of this usage in other settings include:
"The Right Worshipful the Lord Mayor" - used to address or refer to the Mayors of British municipalities.
"The Worshipful Company of ________" - used to refer to any of the Livery Companies of the City of London.
"Worshipful Judge ________" - used in the 1800s to refer to judges and magistrates in many English-speaking countries.