A judicious application of Google-fu to this shows the debate has been going on for some time. Here are some examples from a Masonic paper:
"Early masonic rituals do not show any marked preference for either form. Prichard's Masonry Dissected of 1730 uses the singular four times and the plural once. Three Distinct Knocks published in 1760 has the plural form seven times and the singular twice. Jachin and Boaz which appeared in 1762 shows a slight preference for the singular over the plural by five to four."
http://www.masonicworld.com/education/files/compa.htm
While I still believe the correct term to be the singular from an English language perspective, it is obvious that both forms have been used in Freemasonry for centuries and the "correct" form is that which your Grand Lodge stipulates!
Transmitted via my R5 astromech.
"Early masonic rituals do not show any marked preference for either form. Prichard's Masonry Dissected of 1730 uses the singular four times and the plural once. Three Distinct Knocks published in 1760 has the plural form seven times and the singular twice. Jachin and Boaz which appeared in 1762 shows a slight preference for the singular over the plural by five to four."
http://www.masonicworld.com/education/files/compa.htm
While I still believe the correct term to be the singular from an English language perspective, it is obvious that both forms have been used in Freemasonry for centuries and the "correct" form is that which your Grand Lodge stipulates!
Transmitted via my R5 astromech.