It makes sense that it originated in the home based military aviation training arena and was adopted by the civilian aviation organizations. That gives us a time line of about 1919 (or earlier in the USA and Canadian 1916 -17 training camps) thru to present day. Realistically it could be a (1911-1915) cross over from France, Great Britain or Italy. Sort of a landmark tower in foul weather?
If a pilot has to land in foul weather /fog knowing the height of the squares and the standard amount of squares could give him a realistic expectation of ground level. Then the "follow me" flags on the back of vehicles would be a nautral progression as an airfield identification.