Golf originated in Scotland and the weather there is such that internal fortification is sometimes necessary. Our canny Scottish ancestors found that a jug would last exactly 18 holds, not allowing for spillage (which no Scotsman would allow). 128 = the number of ounces in a gallon, 5 = the number of 5ths in a gallon, 128 divided by 5 = 25.6 ounces in a fifth, 1.4 = the number of ounces in an average drink, 25.6 divided by 1.4 = 18 drinks in one fifth!