I thought the whole octal business stemmed from the time mainframes and minis used 36b, 18b words respectively as 6bit (early mainframe character width) can be

I thought the whole octal business stemmed from the time mainframes and minis used 36b, 18b words respectively as 6bit (early mainframe character width) can be conveniently represented as two digit octal. This changed when computers went 16/32bit and started to use 8bit bytes (and ASCII encoding of characters).